SMITHSONIAN CONTRIBUTIONS TO BOTANY NUMBER 5 Burrett Nelson R W ~ The Woods and Flora of the Florida Keys: c c Pinnatae? SMITHSONIAN INSTITUTION PRESS CITY OF WASHINGTON 1972 A B S T R A C T Barrett Nelson Rock. The Woods and Flora of the Florida Keys: ?Pinnatae.? Smith- sonian Contributions to Botany, number 5 , 35 pages, 35 figures, 1972.-The ?Pin- natae,? comprising six families of woody plants with pinnately compound leaves, is represented on the Florida Keys by at least 16 species. The taxonomic treatment of these families at the ordinal level has been inconsistent. The purpose of this study is to correlate the data derived from intensive study of the xylem anatomy of these 16 species with data from the literature concerning these and other members of the families involved, so that new insight might be gained concerning the taxonomic relationships among these families. This study indicates that the members of the Pinnatae are anatomically homoge- neous. All members possess simple perforation plates, vessel elements having alternate intervascular pitting, fibrous elements with small slitlike simple to vestigially bordered pits, and apotracheal and paratracheal axial parenchyma, or both. Secretory struc- tures, such as crystalliferous idioblasts, parenchymatous cells containing ?gum,? and intercellular canals, are of wide occurrence within the Pinnatae. In addition, many species possess septate fibers and axial parenchyma arranged in aggregate patterns, with banded arrangements being most frequent. There is no anatomical basis for the separation of families into distinct orders in my view. The only separation of families within the Pinnatae suggested by a syn- drome of several unique characters, in addition to those common to all members, is the formation of an Anacardiaceae-Burseraceae complex. The members of the Pinnatae belong to a taxon corresponding well with Cronquist?s Sapindales. Phylogenetically, the Pinnatae constitutes an advanced taxon, based on xylem anatomy. (Scientific Article No. A1731, Contribution No. 4506, of the Maryland Agricultural Experiment Station, Department of Botany.) Oficial publication date is handstamped in a limited number of initial copies and is recorded in the Institution?s annual report, Smithsonian Year. UNITED STATES GOVERNMENT PRINTING OFFICE WASHINGTON : 1972 For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 - Price 50 cents (paper cover) Stock Number 4700-0152 Barrett Nelson ROC^ The Woods and Flora Introduction The Anacardiaceae, Burseraceae, Meliaceae, Ruta- ceae, Sapindaceae, and Simaroubaceae constitute a group of plant families comprising nearly 6,000 species of pantropical distribution. All are charac- terized by plants with pinnately compound leaves. These six families are represented on the Florida Keys by at least 15 genera, each has a single species, except for Zanthoxylum, which has two species there. This investigation is an intensive study of the sec- ondary xylem of these plants (Table 1 ) . According to Brizicky (1962b, 1963)) Picramnia pentandra Swartz (Simaroubaceae) , Melicoccus bijugatus (Sapinda- ceae) , Amyris maritima Jacquin, Zanthoxylum coria- ceum A. Richard, and four naturalized species of Citrus in addition to C. aurantiifolia (Rutaceae) are also to be found on the Florida Keys but are not included in this study. Of the plants studied, only the familial affinity of the genus Suriana has been seriously questioned. The assignment of the othzr genera to families has been more or less generally accepted. Small (1913) placed the genus Dodonaea in his monogeneric Dodonaeaceae. My work has been undertaken to correlate the data derived from the Florida Keys members of these six families with data obtained previously by earlier workers, with the hope that the information gained, although based on a limited number of genera, will give additional insight on the taxonomic relationships of these plants. The taxonomic usefulness of data derived from study of the secondary xylem of dicotyledons, when correlated with morphological, cytological, palyno- Barrett Nelson Rock, Department of Botany, University of Maryland, College Park, Maryland 20742. of the Florida Keys: 6 6 Pinnatae? logical, and other information has been widely ac- knowledged (Chalk 1944, Heimsch 1942, Keck 1957, Stern 1952, Tippo 1946, and others). Comparative anatomical studies of the secondary xylem of some or all of the genera treated in this investigation (Dadswell and Eckersley 1938, Dadswell and Ellis 1939, Dadswell and Ingle 1948, Hess 1946, Heimsch 1942, Kribs 1930, Record 1939, 1941, Webber 1936, 1941) indicate that, on the basis of wood anatomy, a close interrelationship exists among the members of these six families. Plant taxonomists, using morpho- logical characteristics, have also come to the same conclusion. However, arrangement of these families into orders, based in large part upon such morpho- logical characteristics, has been inconsistent. Earlier systems of classification, notably those of Linnaeus (1753), de Candolle (1824-1873), and Bentham and Hooker (1862-1883), were not based on concepts of genetic relatedness as we know them today. As such, the arrangement of the six families within these systems is of little interest, other than historical. It is not surprising, however, that these families were closely grouped by de Candolle and Previous numbers in this series appeared in Tropical Woods (Yale University, School of Forestry) under the running title, ?The Woods and Flora of the Florida Keys?: ?Introduction? by W. L. Stern and G. K. Brizicky, 107:36- 65, 1957; ?Compositae? by S. Carlquist, 109: 1-37, 1958; ?Goodeniaceae? by W. L. Stern and G. K. Brizicky, 109: 38-44, 1958; ?Passifloraceae? by W. L. Stern and G. K. Brizicky, 109345-53, 1958; and ?Wood Anatomy and Phylogeny of Batidaceae? by J. McLaughlin, 110: 1-15, 1959. ?Capparaceae? by W. L. Stern, G. K. Brizicky, and F. N. Tamolang appeared in Contributions from the United States National Herbarium, 34(2) : 25-43, 1963. These studies were initiated through a National Science Foundation grant to William L. Stern in 1955. 1 TABLE 1.-Wood specimens of the Florida Keys ?Pinnatae? examined Collector and Number Lacation and Herbarium Collection Catalog Number Voucher b c a l i t y Species ANACARDIACEAE Metopium t a x i f e m (L.) Kmg & Urban Stern & Brizicky 566 Toxicodendro- radicans (L. ) Kuntze BLTRSEPACEAI Bursera simaruba (L.) Sarg. -- !GLIACW Swietenia mahagani Jacq. RUTACEAE Amyris elernifera L c i t r u s a u r a n t i i f o l i a (L. ) Swing1e Zsnthaxylum f- ( L . ) Sarg. Z. flavum W h l - - SAPINDACEAE 3ar3~0spem:m h s l i c a c a b m I,. Cupania glabra S w . -- Dodonaea viscosa (L.) Jacq. Fxothea paniculata ( A s s . ) Radlk. Hypelate i r i f o l i a t a Sw Sapindus sapanar ia L. SIMeR0UBACEp.E Simarouba glaucB DC. Suriana maritinla L. ~- Stern 2643b Stern 2633 Stern & B r i z i d q 171 Stern 1466 Stern 2624 Sterr. 2616 Sterr. & B r i z i c w 477 Stern 1455 Stern 2614 Stern & b i z i c k y 486 Stern 2653 Stern & Brizicky 514 stern zGn5 sterr., 2eam33, PhiE?S, Rock, & Sweitzer 2761, S te rn 2656 Stern a: Bzizizky 419 Stern 1506 stern 2691 s t e r n 128 Stern & Brizicky 298 Stern 1513 s t e r n , Beaman, Fhipps, Rock, & Sweitzer 2735 Stern & Brizicky 466 Stern 1467 s t e r n 2612 Stern a: Brizicky 526 s t e r n 1468 s t e m 2681 Stern & Brizicky 552 S t e r n 2659 Stem Brizicky 462 S t e m 1497 Stern 2613 Stern & Brizicky 230 s t e r n 1481 stern 2666 Y MARY W R Y Y us None . W Y Y us I W Y Y hWRY Y I rkRY MARY MARY Y 35 MARY Y Y US MARY Y us W R Y Y US . W Y Y VARY Y US m Y US MARY Key Largo Key Largo Key Largo Big P i m Key Windley?s Key Key Largo Key Largo Key la rgo Key Largo Key Largo Key Largo &ey Largo Key Largo Key I a x o 3ahia Honda Key Key largo 3ig Pir.e Key 3ig P k e Key Big Pine Key s ig Pine Key Big Pine Key Big Pine Key Big Fire Key Key la rgo Windley?s Key Key Largo Windley?s Key Windley?s Key Windley?s Key Key largo Key la rgo Key Largo S i R Pine Key Key Largo Big Pine Key Grassy Key Big P i m Key ?Method of c i t a t i o n of wood specimens fa l lows t h a t recam.e?.ded by Stern 8nd Chanbers (l%C). h o d epecimecs, f o r which no ca ta log number i s s ta ted , refer t o f lu id-presemed c o l l e c t i o r s 9t t h e University of Maryland. NUMBER 5 3 Bentham and Hooker, for the similarity of gross morphology is striking. Engler (Engler and Diels 1936) divided these families into two orders : Geraniales and Sapindales. The Rutaceae, Meliaceae, Burseraceae, and Simarou- baceae were placed in the Geraniales; the Anacar- diaceae and Sapindaceae were placed in the Sapin- dales. Assignment of a family to an order was based primarily on the orientation of ovule attachment : family members with epitropous ovules were placed in the Geraniales, while those with apotropous ovules were placed in the Sapindales. The most recent re- vision of Engler?s ?Syllabus der Pflanzenfamilien? (Melchior 1961) redistributes the members of the Geraniales into a revised Geraniales and a newly erected Rutales on the basis of histological differen- tiation and a trend toward zygomorphy in the flowers. The new Geraniales and Rutales are still segregated from the Sapindales on the basis of ovule attach- ment. The families concerned with in this study which were included in the Geraniales are now placed in the Rutales. The phylogenetic schemes used by Hutchinson, Hallier, and others, de-emphasized the ovular orien- tation of Engler. Hutchinson (1926) erected three orders to account for these families, separating them largely on the presence or absence of gland-dotted (pellucid dots) leaves (Figure 5 ) . Those families often having members with gland-dotted leaves were placed in his Rutales (containing the Rutaceae, Sim- aroubaceae, and Burseraceae) , while those families without gland-dotted leaves were placed either in the Meliales or Sapindales. The Meliales (containing the Meliaceae) is characterized by members having a stamina1 tube which is lacking in members of the Sapindales (containing the Anacardiaceae and Sap- indaceae) . All of these orders are within Hutchinson?s arborescent line of evolution. These three orders plus the order Juglandales were grouped by Hutchinson in the subphylum ?Pinnatae.? The Juglandales was later dropped from this subphylum (Hutchinson 1959). Hallier?s earlier treatment (1905) placed all six families in his large cohort, Rosales, with the note that it would be further subdivided after ?. . . more exhaustive examination.? Hallier ( 1912) later combined the members of the Anacardiaceae and Burseraceae into a single family, the Terebinthaceae, which he included in his Rutales, along with Ruta- ceae, Meliaceae, and Simaroubaceae. The Sapinda- ceae was placed in his Sapindales. Wettstein (1935) included all six families in his Terebinthales. A survey of recently proposed phylogenetic systems of classification reveals that the treatment of these families is still not uniform. Cronquist (1968) assigns the six ?mutually interrelated? families to his Sapin- dales, citing Heimsch?s work (1942) as a primary reason. Takhtajan (1966) places the Sapindaceae in his Sapindales, moving the remainder of the families into his Rutales. Both orders are placed in the super- order Rutinae (which also includes his Geraniales and Polygalales). Thorne (1968) places all the fam- ilies in his Rutales, grouping the families into sub- orders Rutineae (corresponding to Takhtajan?s Ru- tales) and Sapindineae (containing the Sapinda- ceae). (Table 2 offers a summary of the taxonomic treatment of these six families.) Suriana maritima Linnaeus, generally considered within the Simaroubaceae, is seen by Gutzwiller (1961), Jadin (1901), Record and Hess (1943), Small (1911), Thorne (1968), Wilson (1911), and others, as constituting a distinct monotypic family, the Surianaceae. Cronquist ( 1968) accepts Gutzwil- ler?s exclusion of Suriana from the Simaroubaceae, but chooses to place this genus with Stylobasium in his (Cronquist?s) Stylobasiaceae. This family is in- cluded in Cronquist?s Sapindales. On the basis of wood anatomy, Webber (1936) states that such a separation of Suriana from the Simaroubaceae is not justified. The distribution and habit of each species dealt with in this study vary widely and are listed sepa- rately. Data concerning number of species, distribu- tion, and habit were obtained primarily from Brizicky (1962a, 1962b, 1962c, 1963). The species are listed by family. The collection site of each specimen is indicated in Table 1. ANACARDIACEAE. Metopium is a genus of three species, occurring in the West Indies, southern Florida and the Florida Keys, British Honduras, Guatemala, and southern Mexico. Metopium toxiferum (L.) Krug and Urban, a West Indian species, is found in the hammocks, pinelands, and coastal dunes in south- ern Florida and the Florida Keys. It occurs as a large tree in the hammocks and as a shrub in the pinelands throughout the Florida Keys. Toxicodendron is a largely north temperate zone genus of approximately 15 species of North American and eastern Asiatic distribution. Toxicodendron ra- 4 SMITHSONIAN CONTRIBUTIONS TO BOTANY TABLE 2.--Com~arison of taxonomic treatments Order Sapindales Stylabasiaceae' Sapindaceae Furseraceae Anacardisceae Simaroubaceae Rutaceae Meliaceae h g l e r (Melchior 19647 l rder Rutalesb Suborder Rutineae Rutaceae Simaroubaceae Eurseracese Meliaceae k d e r Sapindales Suborder Anacardineae h a c a r d i a c e a e Suborder Sapindineae Sapindsceae Hutchinson (1959) ,ubphylw,. HcnataeC Order. Rutales Futaceae Simaroubaceae Bursereceae Order Meliales Meliaceae Order Sapindales Sapindaceae Anacardiaceae Tskhtajan (1966) superorder Rutinae' Order Rlteles Anacaraiaceae Burseraceae Sinaroubaceae Rutaceae Meliaceae Order %piridales Sapindaceae Thorne (1968) luperarder. Rutiflarse Order Futales Suborder. Rutineae Rutaceae SLmaroubaceae surianaceae Meliaceae 3;rseraceae h a c a r d i a c e a e Suborder. Sapindineae Sapindaceae aInc1uaes - t h i s most recent revision of Engler's system (Melchior l % k ) the o lder Geraniales has been subdivided i n t o a revised Ceraniales and B newly erec ted Rutales (conta in ing those fami l ies l i s t e d above i n addi t ion to others 1. 'This subphylum previously included t h e order Juglandales (1926 ) . 'ffeviously t h e silperorder Einnatae . dicans (L.) Kuntze (Figure 1) is widely distributed in woods, thickets, fencerows, and swamps through- out most of southern Canada, the United States, northern Mexico, and the West I n d k 2 I t occurs as a woody vine throughout its range. BURSERACEAE. Bursera is a genus of approxi- mately 100 species, distributed throughout tropical and subtropical America. Bursera simaruba (L.) Sargent (Figures 2, 3) is found in southern Florida and the Florida Keys, the West Indies, southern Mexico, Central America, and northern South Amer- ica. It occurs as a large tree, primarily in the ham- mock forests throughout the Florida Keys. Swietenia, a genus of at least three species, occurs in southern Florida and the Florida Keys, the West Indies, Mexico, Central America, Colombia, Venezuela, and the upper Amazonian region. Swietenia mahagoni Jacquin (Figure 4) is found in the West Indies, southern Florida and the Florida Keys. On the Florida Keys it occurs in the hammock forests. It is a large tree throughout its range. Amyris is a genus of approximately 20 species, occurring in southern Florida (including the Florida Keys) and Texas, the West Indies, Cen- tral America, and northern South America. Amyris MELIACEAE. RUTACEAE. Toxicodendron is recognized as distinct from Rhus, primarily on the basis of Barkley's monograph (1937). elemifera Linnaeus is primarily a West Indian species, occurring also in southern peninsular Florida and the Florida Keys. I t ranges in habit from a shrub to a small tree (up to 50 feet tall, with trunks up to a foot in diameter), and occurs in the hammock forests throughout the Keys. Citrus is a highly polymorphic genus with an uncertain number of species (16 minimum and possibly 145 maximum, Brizicky 1962a), native to southern and southeastern Asia and Malaysia. Sev- eral species are widely cultivated and have escaped to all warm regions of the world (Brizicky 1962a). Five species are recorded as more or less naturalized throughout southern Florida and the Florida Keys. Citrus ourantiifolia (L.) Swingle, the lime (the single species of Citrus collected), is a tree native to the East Indian Archipelago. I t occurs on the Florida Keys along roadsides and in secondary woods (hammock forests). Zanthoxylum, a genus of some 215 species, is mainly pantropical in distribution (Brizicky 1962a), with several species extending into temperate North America and eastern Asia.3 Both of the species en- 'According to Record and Hess (1943) , the genus Zanthoxylum comprises only 15 species, all of north-tem- perate distribution, while the genus Fagara comprises ap- proximately 200 pantropical species. Brizicky ( 1962a) con- siders Fagara as a synonym for the older Zanthoxylum. NUMBER 5 5 countered in this study are considered native to the West Indies (Brizicky 1962a). Zanthoxylum fagara (L.) Sargent occurs in central and southern Florida, including the Florida Keys, southern Texas, the West Indies, Mexico, Central America, and South America. I t occurs as an armed (spined) shrub oi small tree throughout its range. Zanthoxylum flavum Vahl occurs as an unarmed small tree on the lower Florida Keys (specifically Bahia Honda Key State Park) and the West Indies. Both species occur in hammock forests. SAPINDACEAE. Cardiospermum, a genus of ap- proximately 12 species, is primarily of tropical American distribution, with one species occurring in tropical West Africa and one ill-defined species (Cardiospermum halicacabum L.4) of pantropical distribution. Cardiospermum halicacabum (Figure 8 ) , a woody perennial vine, occurs in the hammock forests on the Florida Keys. Cupania is a tropical American genus of approxi- mately 45 species and extends from Argentina and Peru north to Mexico and into southern Florida, the Florida Keys, and the West Indies. Cupania glabra Swartz (Figure 9) occurs in the West Indies, the Florida Keys, Mexico, and Central America as far south as Costa Rica. I t is a small tree of the ham- mock forests, occurring in Watson?s Hammock on Big Pine Key. Dodonaea is primarily an Australian genus of ap- proximately 60 species. One species occurs in Mada- gascar, three occur in Hawaii, and one [Dodonaea viscosa (L.) Jacquin] is reported as pantropical in distribution. Dodonaea viscosa5 occurs as a small tree ? The treatment of the species Cardiospermum halicaca- bum accepted in this study is as follows: C. halicacabum comprises at least three varieties-halicacaburn, microcarpum (syn. C. microcarpum H.B.K.) , and corindum (syn. C. corindum L.; C. keyense Small)-each of which is con- sidered by some authors (Brizicky 1963) as constituting a separate pantropical species. All three varieties are reported as occurring on the Florida Keys. ?Brizicky (1963) refers to the pantropical species as Dodonaea viscosa ( L . ) Jacquin, noting that this species in- cludes D. jamaicensis de Candolle and D. microcarya Small, tentatively accepting SherfT?s concept of a single species (D. viscosa) having three distinct pantropical varieties. Sherff asserts that all of these varieties occur in Florida. Brizicky states, however, that inadequate data make ?. . . im- possible any conclusion regarding the nature and delimita- tion of infraspecific categories of D . uiFcosa.? Therefore, throughout this paper, the Florida Keys Dodonaea is refer- red to as D. viscosa. in the hammock forests and adjacent pinelands of the Florida Keys. Exothea is a tropical American genus of three spe- cies, ranging from the West Indies, southern Florida, Mexico and Central America, south to Costa Rica. Exothea paniculata (Jussieu) Radlkofer occurs as a small tree in the hammock forests and on calcareous soils and shell mounds in southern peninsular Florida, the Florida Keys, the West Indies, and Guatemala. Hypelate, a genus comprising a single species, H . trifoliata Swartz, occurs as a shrub or small tree in the hammock forests (and rarely the pinelands of Big Pine Key) of the Florida Keys and the West Indies. Sapindus is largely a tropical genus of approxi- mately 13 species, three of which are distributed in the Americas, with the remainder found in eastern and southeastern Asia, Oceania exclusive of Austra- lia, and Hawaii. At least two of these species are extratropical. The primarily tropical American spe- cies, S. saponaria Linnaeus (Figures 6, 7 ) , occurs as a tree from Argentina, north into Mexico, the West Indies, southern Florida, and the Florida Keys. I t is a member of the hammock forest flora on the Florida Keys. Simarouba is a widely distrib- uted tropical American genus comprising from six to nine species. Sirnarouba glauca DeCandolle (Fig- ure 10) occurs as a tree in southern Florida and the Florida Keys, the West Indies, southern Mexico, Central America, and part of South America. I t is an inhabitant of the hammock forests on the Florida Keys. Suriana is a monotypic genus of pantropical dis- tribution. The single species, S. maritima L. (Figure 11) is a small to large shrub (occasionally a small tree) of the strand vegetation, occurring along sea- coasts throughout its range. SIMAROUBACEAE. Materials and Methods Specimens studied in this investigation are listed in Table 1. Dried wood specimens were obtained from Dr. William L. Stern. Specimens bearing catalog numbers of the Record Memorial Collection, Yale University School of Forestry ( Y W ) ~ , and the Na- ? The Samuel James Record Memorial Collection, origi- nally housed at the Yale University School of Forestry, was transferred to the U.S. Forest Products Laboratory in Mad- 6 SMITHSONIAN CONTRIBUTIONS TO BOTANY tional Collection of Woods, Smithsonian Institution (USw) , were available as prepared slides. In addi- tion, fluid-preserved specimens bearing Stern collec- tion numbers 2612 through 2764 were utilized (see Table 1 ) . All wood samples were collected from mature stems and are documented with herbarium vouchers, with the exception of Bursera sirnaruba Sargent, Stern 2624. Microscope slides of specimens bearing Yale or Smithsonian catalog numbers had been previously prepared from unembedded, dried wood samples. The fluid-preserved specimens were embedded in celloidin prior to sectioning. All slides prepared spe- cifically for this study from fluid-preserved material collected by Stern were sectioned on a sliding micro- tome. All transverse sections were cut a t 20p, while radial and tangential sections were cut a t 15p, 20p, and 30p to provide different thicknesses for optimum study of all cells and tissues. The sections were stained in safranin and Heidenhain?s iron-alum haematoxylin, dehydrated and cleared following standard microtechnical procedures, and mounted in Canada balsam. Exceptionally hard woods were soft- ened prior to sectioning, either in hydrofluoric acid, as outlined in Sass (1958), or by boiling in Aerosol OT solution in a reflux apparatus (a modification of the procedure outlined by Ayensu 1967). Macerations were prepared following a variation of Jeffrey?s method. The original method, outlined in Johansen ( 1940), was modified in the following man- ner: tertiary butyl alcohol was used as the dehydrant and, upon complete dehydration, a small amount of stained cellular material was taken directly from the tertiary butyl alcohol and placed into a watch crystal containing a mixture of xylene and Canada balsam of mounting consistency. The mass of cellular mate- rial was then spread throughout the mounting me- dium by gently mixing with a glass rod. A few drops of this mixture were then placed on a microscope slide and a cover slip added. Selection of the diagnostic characters to be included in the descriptions of each species was made from those suggested by Tippo (1941). Measurements of the length of both fibrous elements and vessel ele- ison, Wisconsin, in December 1969. I t is distinguished from other wood collections in the Laboratory through the abbre- viation SJRw. Original wood collections at the Laboratory bear the abbreviation MADw ; the Record Collection for- merly carried the abbreviation Yw. ments were made from macerated material. Measure- ments of pore distribution, pore diameter, and end wall angle were made from sectioned material. All measurements are recorded in microns ( p ) . Fibrous elements were measured using a Bausch and Lomb Tri-Simplex microprojector, except in a few cases where, because of cellular breakage, accu- rate measurement required the higher magnification and resolution available only through the use of a compound microscope. Vessel element lengths were measured with both the microprojector and the microscope, the latter was used when the small size of the vessel elements prohibited accurate measure- ment on the projector. The total length (tail to tail) of vessel elements was measured, following the sug- gestions of Chalk and Chattaway (1934, 1935). Tangential pore diameters were measured from outside wall to outside wall. Only solitary pores were measured except in species where, because of the low percentage of solitary pores, measurement of the tan- gential diameters of pores arranged in radial multiples was required. Pore distribution was determined from transverse sections, while vessel element end wall in- clination was measured on tangential sections. In measuring the lengths of the fibrous elements and vessel elements, pore diameter, and inclination of vessel element end walls, a total of 50 random measurements of each character was made for each species. From these measurements, a range, a most frequent range (within which at least 50 percent of the measurements made occur; hereafter abbre- viated MFR) , and a mean (average) were calculated, except for the inclination of end walls, where only a mean was calculated. Pore distribution was determined by recording the total number of solitary pores, radial multiples, and pore clusters seen in a given field of view. Ten fields were observed, and the total number of pores in each distribution type was converted to a percentage of the total number for all categories. In members of the Rutaceae, pore chains in addition to radial multiples are observed. Because of intergrades be- tween chains and multiples, and the difficulty in dis- tinguishing between each type, the pores of either type are reported only as radially oriented (Table The terminology used in this investigation generally follows that suggested by the Committee on Nomen- clature, International Association of Wood Anato- 3). NUMBER 5 55-90 2C-75 83-105 too-163 7 2-7 1 - 5 1-3 3-8 TABLE 3.-Pore arrangement, diameter, and wall thickness 65-10c 45-85 50-7C POFE DISTRIBUTION ( p e r c e n t ) 4-8 2-12 2-7 SFZCIES ANACARDIACEAE Metopiwn toxiferum Taxicodendran radicans SWSERACE.45 Bursera sinaruba -__ MELLACEAE Swietenia mahagoni RLTTACEAI Amyris elemifera C i t m s a u r a n r i i f o l i a Zamhoxylum fasara 2 . flwm SAPIhQACEAE - - Cardiospermum halicacaburr. 83-125 75-95 60-90 60-85 45-73 85-110 Cupsnia glabra Cadonaea v iscasa Exathea panicu la ta Hypelate t r i f o l i a t a Sapindus saponaria -- SIMAROUBACEAE Simarouba glauca Suriana maritime. -- 4-13 2-7 3-7 2-8 3-7 2-5 S o l i t a r y 67 80 70 68 53 70 55 42 75 35 43 50 59 78 40 41 m l t i p l e s Radially Oriented Clus te rs D Av g - - 78 52 88 -36 53 78 63 58 3Zd -02 78 72 71 58 99 -75 58 - IETER Range 40-110 15-110 45-110 65-220 30-55 30-110 30-100 40-85 20-50 60-145 30-105 50-100 50-95 3C-80 40-150 85-260 30-85 m 1 Rangeo ?Numbers i n parentheses i n d i c a t e t h e range of t h e number of pores Pound i n each category. b a l l s between pores i n . rad ia l mul t ip les and c l u s t e r s are t h e t h i c k e s t . CPore d i s t r i b u t i o n reported a8 ? r a d i a l l y or ien ted? because Of d i f f i c u l t y i n d i f f e r e n t i a t i n g between radial mult ip les and cha ins . Gxly i n t h e case of Amyris elemifera a re t h e majority of t h e r a d i a l l y or ien ted pores i n d i s t i n c t cha ins . dSmal l pores (see d e s c r i p t i o n ) . mists, International Glossary of Terms Used in Wood Anatomy (1957), hereafter referred to as the IAWA Glossary. General terms used in describing relative sizes of structures (e.g., intervascular pit sizes and fibrous element, cell wall thickness) are those sug- gested by Record and Chattaway (1939). The terms ?fibrous elements? and ?imperforate tracheary elements? are used here interchangeably and refer to the prosenchymatous cell types commonly referred to as ?fibers.? No attempt was made to designate such fibrous elements as either fiber-tra- ? I n the parlance of ?wood technology? and ?forest products,? ?fibers? also include the tracheids of gymno- sperms. cheids or libriform wood fibers, because of the tenuous nature of the pitting encountered in the species studied. In describing the simple pits commonly found in the parenchymatous cell types encountered in the woods under study, the term ?fenestriform? is used. This term, meaning ?windowlike,? is used to describe any enlarged, oval to rectangular pit. These enlarged pits are considerably broader than the intervascular pits in the species being described. The fenestriform pits most frequently seen in this study are the en- larged simple components of a half-bordered, vessel to parenchyma pit-pair. In some species both com- ponents of vessel to parenchyma pit-pairs are fenestri- 8 SMITHSONIAN CONTRIBUTIONS TO BOTANY form in nature. Since the simple fenestriform pits are generally larger than the bordered pit of a half- bordered pit-pair, a single fenestriform pit will fre- quently subtend two or more bordered pits, resulting in unilaterally compound pitting. Because of the ambiguity, awkwardness, and lack of precision involved in employing only names to categorize vascular rays (Kribs 1935), a description of the ray tissue of each species is given. The terms ?homocellular? and ?heterocellular? are used in the literal sense. Rays comprising only a single cell type (for example, a ray which consists only of procumbent cells) are referred to as homocellular. A ray con- taining two or more cell types, even though one type may be of only rare occurrence, is referred to as heterocellular. Since varying degrees of the hetero- cellular type of ray occur in the woods studied, refer- ence to the predominant cell type or types is given in each description. In the following anatomical descriptions, charac- ters common to all the species studied are included in an initial description. The descriptions of the in- dividual species which follow this are arranged ac- cording to family. The arrangement of both families and the genera within each family is alphabetical. Table 3 contains numerical data concerning the pore distribution, pore diameters, and vessel wall thickness of each species. Table 4 is a summary of pertinent anatomical data obtained from each species and is included in order to facilitate comparison. Anatomical Descriptions of the Woods of ?Pinnatae? Where growth rings are present, the wood in all specimens studied is diffuse-porous (Figure 16) , with the exception of Toxicodendron radicans, which is questionably diffuse-porous (Figure 19) . All perfora- tions are simple (Figure 32), with the exception of a single multiple perforation observed in Metopium toxiferum. Intervascular pitting is alternate in all species (Figures 30, 31 ) . Scalariform-like intervascular pit- ting produced by coalescence of adjacent pits and unilaterally compound intervascular pitting (Figure 31) occur to some extent in each species. Fenestri- form pits occur in the axial parenchyma and ray parenchyma of each species, while in Bursera sima- ruba, Metopium toxiferum, and Toxicodendron radicans both components of vessel to parenchyma pit-pairs are commonly fenestriform (Figure 32) . Unilaterally compound vessel to parenchyma pitting occurs in all species. The fibrous elements of all species studied have oval to slitlike simple or slightly bordered pits pre- dominating on their radial walls (Figures 28, 2 9 ) . The slitlike inner apertures of any given pit-pair may be either crossed at angles to one another, or directly superposed. Both configurations are frequently ob- served on a single specimen. Axial parenchyma is present in all species. Vascular tracheids and dis- junctive paratracheal parenchyma cells are found in all species. ANACARDIACEAE Metopium toxiferum (L.) Krug and Urban: Faint growth rings are present. The pores are angular to rounded, with vessel element walls varying in thickness from 2p to 7p. Vessel element length averages 375p, with a range of 19Op to 670p and a MFR of 330p to 450p. Per- forations are simple, with the single exception of a multiple perforation observed in maceration. The arrangement of perforations in this instance is such that neither the term reticulate nor foraminate is accurately descriptive. I t should be noted that be- cause of the fenestriform nature of vessel wall pits involved in vessel to parenchyma .pitting, description of this perforation plate as multiple may not be ac- curate. The structure seen may actually be a collec- tion of such fenestriform vessel wall pits, arranged at the end of the vessel element in such a manner that the impression of a multiple perforation is given. Vessel element end walls are inclined at an average of 44?. In general, the vessels are ligulate. Intervascular pitting comprises medium-sized pits ranging from 7p to lop in diameter. Pit borders are round to somewhat angular; pit apertures are oval and included within the borders. Both vessel to axial parenchyma pitting and vessel to ray parenchyma pitting are fenestriform in nature, both members of a vessel to parenchyma pit-pair are oval to somewhat angular and simple. The imperforate tracheary elements are nonseptate. Fibrous elements are gelatinous in nature (Figure 34) , and, as such, two measurements of wall thickness were made. The rigid lignified portion of the sec- NUMBER 5 9 ondary wall is from l p to 3p thick while the com- bination of rigid and nonrigid secondary walls seldom exceeds 6p. As such, the wall thickness (combined) ranges from thin to very thick. The average length of the fibrous elements is 683p, with a range of 330p to 970p and a MFR of 560p to 860p. Vascular rays are predominantly bi- and triseriate. Some uniseriates are present and a few rays up to five cells wide are seen. These may contain horizontal intercellular canals. All rays are heterocellular, com- prising upright, square, and procumbent cell types. The bi- and triseriate rays frequently possess uniseri- ate wings of from 2 to 4 rows of square and upright cells, or both, the remainder of the ray comprising procumbent cells. Many of the uniseriate rays appear to be composed largely of square and upright cells, or both. The uniseriate rays range from 1 to 8 or more cells in height, while the bi- and triseriate rays are up to 20 cells (400p) or more in height. Starch occurs in many of the ray cells. The horizontal intercellular canals seen in the rays of this species are of infrequent occurrence in Stern 2643, but rather frequent in Stern @ Brizicky 556. The canals are surrounded by an epithelial lining (1 to 2 cells thick) composed of small, square to angular cells with thin isotropic (optically inactive) cell walls. The cells external to the epithelial lining are of similar shape and size, but with somewhat thicker, optically anisotropic cell walls. These cells tend to intergrade with the larger, typical procumbent cells. The canals seen in Stern 2643 are apparently at an early stage of development, possessing small inter- cellular spaces or canals, while those seen in Stern @ Brizicky 556 are of a later stage of development, having massive intercellular spaces or canals. Many of these older canals lack any organized epithelial layer (apparently due to lysigeny). In the latter specimen, the canals are often nearly as wide as the ray in which they occur. In both specimens a dense, rather darkly staining substance is found in many of the canals, in addition to remnants of epithelial cell walls. It is apparent that these canals are secretory in nature. Axial parenchyma is present in both apotracheal and paratracheal arrangements. Apotracheal paren- chyma forms irregularly spaced bands which vary in width from 1 or 2 cells to 10 or more cells wide. Bands are independent of growth rings. Paratracheal parenchyma is aliform to confluent, leading to some localized banding. All the axial parenchyma cell types frequently contain starch grains. Crystalliferous strands are absent. Thin-walled tyloses are seen extending into the vessels from both axial and ray parenchyma (Figure 3 4 ) . In longitudinal section, a high percentage of the fenestriform vessel to ray pits are sites of tylosis for- mation. Toxicodendron radicans (L.) Kuntze : The wood is diffuse-porous (Figure 19), although the outer growth rings tend to be ring-porous ; faint growth rings are present. The pores are circular to somewhat angular, with walls ranging in thickness from lp to 5p. Tangential pore diameters range from 15p to 11Op. A study of macerated material, however, re- veals a number of smaller vessel elements, having diameters of less than 15p (as measured on macerated material). These vessels could not be included in the measurements of diameters in transverse section, be- cause they are not readily distinguishable from im- perforate tracheary elements. Vessel element length averages 250p, with a range of 120p to 360p and a MFR of l 6 0 p to 300p. Vessel element end walls are inclined at an average of 41?. The vessel elements are generally ligulate. Intervascular pitting comprises small bordered pits ranging in size from 4p to 6p in diameter. The pits, generally restricted to the ends of the vessel elements (pitting on the body of the vessel elements is rela- tively infrequent, because of the high percentage of solitary pores) , possess circular to lenticular apertures included within rounded to angular borders. Vessel to axial parenchyma pitting comprises half- bordered to simple pit-pairs. The component pits of a simple pit-pair, in the vessel element wall and the axial parenchyma wall, are both fenestriform in nature. Half-bordered pit-pairs are rather infrequent, the bordered pit of the vessel element wall generally having large lenticular apertures extending to lentic- ular borders. These bordered pits are generally larger than the intervascular bordered pits and intergrade with the fenestriform simple vessel element pits. Ves- sel to ray parenchyma pitting is very infrequent. When present, it resembles the vessel to axial paren- chyma pitting. The imperforate tracheary elements are septate, each cell having a single septum. Fiber walls vary in thickness from 1p to 5 p and range from very thin to thick. A study of macerated material reveals that 10 SMITHSONIAN CONTRIBUTIONS TO BOTANY the fibrous elements may have either attenuated or truncate end walls. Fibrous elements contain mas- sive amounts of starch. The average length of the fibrous elements is 374p, with a range of 230p to 560p and a MFR of 300p to 440p. Vascular rays are uniseriate and biseriate, although in some cases, a portion of a biseriate ray may be up to three cells wide. Square and upright cell types occur most frequently, while the procumbent cell type is rare. The cell type found in any given horizon- tal row is frequently constant, with one row composed entirely of upright cells while another is composed of square cells. The occurrence of two cell types within the same horizontal row is relatively infre- quent. Arrangement of cell types does not follow a pattern. The uniseriate rays vary in height from 2 cells to 30 cells or more. Approximately 50 percent of the ray cells contain a dark-staining substance of unknown composition. Ray cells generally contain large amounts of starch. Axial parenchyma is present in both apotracheal and paratracheal arrangement. Diffuse parenchyma apparently comprises noncrystalliferous strands. Since the fibrous elements of this species are living (septate and store starch), it was difficult to determine wheth- er cells, seen in either transverse or longitudinal sec- tion, were axial parenchyma cells or fibers. Since the other parenchymatous cells (paratracheal paren- chyma and ray parenchyma) frequently contained a dark-staining substance, this character was used as the distinguishing criterion ; cells containing the dark- stained substance, when viewed in transverse section, were interpreted as diffuse parenchyma. The para- tracheal parenchyma is scanty vasicentric to vasi- centric, and, as mentioned previously, frequently con- tains a dark-staining substance similar to that seen in the ray tissue. A large number of small, thin-walled tyloses are present in many of the vessel elements. The tyloses contain the dark-staining substance seen in the para- tracheal parenchyma cells. This is to be expected, since tyloses are extensions of parenchyma cells into the vessel lumen. BURSERACEAE Bursera simaruba (L.) Sargent: Growth rings are absent. The pores are somewhat angular and have walls l p to 3p thick. Vessel element length averages 531p and ranges from 300p to 770p; the MFR is 495p to 700p. Ves- sel element end walls are inclined at an average of 48'. The vessels may be either ligulate or eligulate. Intervascular pitting comprises medium-sized pits ranging from 7p to l op in diameter. The pit aper- tures are lenticular and included within polygonal pit borders. Vessel to axial parenchyma pitting is rare because of the scarcity of paratracheal parenchyma. Where it occurs, it is sporadic and irregular to alternate and larger than the intervascular pitting. Vessel to ray pitting differs from the above in that it is var- iable in form, ranging from large, generally rectangu- lar fenestriform pits to small, oval pits (Figure 3 2 ) . Both components of the former type of vessel to ray parenchyma pit-pair are fenestriform in nature. Both vessel to axial parenchyma pitting and vessel to ray parenchyma pitting are half-bordered. The imperforate tracheary elements are septate, having from 3 to 8 septa per cell, 3 being the most common. Fibrous elements in Stern 2624 contain massive amounts of starch (Figures 12, 1 3 ) ; starch grains are also seen in Stern 1466. Wall thickness of fibrous elements may be classified as very thin, 2p to 4p thick. The average length of the fibrous elements is 809p, the range 440p to 116Op and the MFR 730p to 950p. Vascular rays are predominantly multiseriate ; some uniseriate and biseriate rays are seen. All rays are heterocellular, although some of the uniseriate rays appear to be homocellular when seen in tangential section. A survey of 10 radial sections, however, did not reveal such homocellular rays. This is apparently related to the nature of cell arrangement. In radial section, there are no horizontal rows consisting of only one type of ray cell. Those rows containing procumbent cells also contain square and upright cells, or both. Tangential sections of the same ray taken at different points would appear to be homocel- lular at one point and heterocellular at the other. The height of the uniseriate rays is up to 350p (20 cells). These are f a r less frequent in occurrence than are the multiseriate rays. Multiseriate rays are up to 500p (30 cells) in height and up to loop in width. The body of the multiseri- ate ray is composed of procumbent cells. These rays generally have uniseriate wings, 1 to 3 cells high, composed of upright and square cells, or both. The NUMBER 5 11 rows of procumbent ray cells are uniform, as is gen- erally true of the rows of upright and square cells of the vertical wings. The upright and square ray cells of this ray tissue frequently contain optically anisotropic, prismatic crystals and starch grains. Horizontal intercellular canals are seen in many of the multiseriate rays (Figure 24). These canals are circular in cross section (as seen in tangential section) and surrounded (lined) with thin-walled epithelial cells. The walls of the epithelial cells are optically isotropic (optkally inactive when viewed under crossed nicols) . The arrangement of axial parenchyma is difficult to determine, because of the difficulty in distinguish- ing between axial parenchyma cells and the thin- walled, septate, living fibrous elements. As mentioned previously, the fibrous elements store starch and, as such, carry on one of the functions of axial paren- chyma. Determination of the presence of axial paren- chyma was made only through study of macerations. Distinction between fibrous elements and axial paren- chyma cells in macerated material was based on the pitting and on the cell wall configuration: the trans- verse, truncate, horizontal end walls of the paren- chyma cells and the septa of the attenuated fibers. The axial parenchyma seen in macerations may be classified as scanty vasicentric. Apotracheal paren- chyma may also be present but is not distinguishable in transverse section. MELIACEAE Swietenia mahagoni Jacquin : Growth rings are present. Pores are rounded to somewhat angular with vessel element walls varying in thickness from 3p to 8p. Vessel element length averages 437p, with a range of 200p to 720p and a MFR of 390p to 515p.. Ves- sel efement end walls are inclined at an average of 62'. Vessel elements may be either ligulate or eligu- late. Intervascular pitting comprises minute bordered pits ranging in size from 2p to 3p in diameter. Pit borders are rounded to angular; pit apertures are lenticular to oval and are included within the bor- ders. Vessel to axial parenchyma pitting and vessel to ray parenchyma pitting are very similar in size, shape, and arrangement. Both types of vessel to parenchyma pitting are half-bordered. The bor- dered pits of the vessel wall are arranged in an alternate pattern, these pits coinciding in shape and size to intervascular pits. The simple pits of the parenchyma walls are oval to elongate and often fenestriform in nature. Imperforate tracheary elements are septate, having a wall thickness that varies from 2p to 7p, and ranges from thin to thick. Septa are thin and there are two per cell. The average length of the fibrous ele- ments is 981p, with a range of 650p to 1250p and a MFR of 880p to 1160p. The vascular rays are uniseriate to multiseriate, with rays infrequently up to five cells wide; 3- and 4-seriate rays are the most frequent. All rays are heterocellular. The infrequent uniseriate rays are short, ranging from a single cell to eight or more cells in height, and composed almost entirely of square and upright cells, or both. Biseriate rays are longer than uniseriate rays, ranging from 5 to 15 or more cells in height, and composed of the same cell types seen in the multiseriate rays. Multiseriate rays range in height from 10 cells (250p) to 30 cells (700p) or more, the longer rays generally resulting from vertical fusion of two rays. Bi- and multiseriate rays comprise procumbent, square, and upright cell types. The procumbent cell type generally makes up the multiseriate portion of a given ray, while the square and upright cell types comprise the one- to many- celled uniseriate wings or margins (Figure 2 2 ) . Many ray cells contain an opaque, dark-staining substance of unknown composition. Most ray cells contain starch. Marginal cells are frequently crystalliferous idioblasts. The ray tissue is storied. Axial parenchyma occurs in both apotracheal and paratracheal arrangement. Apotracheal parenchyma is present mainly as marginal bands (initial). Some diffuse parenchyma is also present. Both types of apotracheal parenchyma cells contain starch; either may be crystalliferous, the occurrence of crystal- liferous idioblasts is infrequent and random. Crystal- liferous strands are not present. The paratracheal parenchyma is scanty vasicentric to vasicentric. Both types of axial parenchyma cells frequently contain the same dark-staining substance reported in the ray cells. Vessels generally contain this dark-staining opaque substance also. The vessel elements tend to be storied in addition to the rays. 12 SMITHSONIAN CONTRIBUTIONS TO BOTANY RUTACEAE Amyris elemifera Linnaeus: Growth rings are pres- ent, but not distinct. Pores are rounded in cross sec- tion, and have walls 4p to 8p thick. Chains are the predominant, radially oriented, pore group. Vessel element length average 2 5 0 ~ , with a range of 110p to 350p and a MFR of 220p to 330p. Ves- sel element end walls are inclined at an average of 55?. The vessel elements are generally ligulate. Intervascular pitting comprises minute bordered pits ranging from 3p to 4p in diameter. Pit apertures are slitlike to oval and included within the circular pit borders. Vessel to axial parenchyma pitting is rare, owing to the scarcity of paratracheal axial paren- chyma; where it occurs, it is alternate. Vessel to ray parenchyma pitting is alternate. In both types of ves- sel to parenchyma pitting, the pit-pairs are half- bordered; the vessel pits are similar in size and shape to the intervascular pits described above, and the parenchyma pits are fenestriform and simple. Imperforate tracheary elements are nonseptate, having thick cell walls 3p to 7p in thickness. The aveage length of these fibrous elements is 443p, with a range of 270,~ to 660p and a MFR of 375p to 5301. Vascular rays are uniseriate and homocellular, all cells are procumbent. Although the orientation of individual ray parenchyma cells is horizontal in all cases, cell length varies, and in some instances, some cells in a horizontal row are nearly square. However, since these ?square? cells are not a consistent charac- ter, either in their occurrence or their arrangement, I feel the designation of ?homocellular? is justified. Rays average from 3 to 10 cells in height, rarely up to 19 cells (200p) high. Axial parenchyma is present as diffuse and banded apotracheal parenchyma and as scanty paratracheal parenchyma. The banded apotracheal parenchyma is 1 to 3 cells wide and continuous; the diffuse paren- chyma is present as crystalliferous strands compris- ing 2 to 8 cells (as viewed in tangential section). The crystalliferous parenchyma cells (idioblasts) are much enlarged. No starch grains were seen, because of the acid-softening treatment. Small thin-walled tyloses are present (Figure 33) . An amorphous material is seen in some vessels, per- haps because of gummosis of the parenchyma cells forming the tyloses. Citrus aurantiifolia (L.) Swingle: Growth rings are present. The pores are circular, with walls rang- ing from 4p. to 8p thick. Radial multiples are the predominant, radially oriented, pore group. Vessel element length averages 273p, with a range of 150p to 420p and a MFR of 235p to 340p. Ves- sel element end walls are inclined at an average of 58?. Vessel elements may be ligulate or eligulate. Intervascular pitting consists of small pits, ranging from 4p to 6.p in diameter. Pit apertures are rounded to oval and included within round to polygonal bor- ders. Vessel to axial parenchyma pitting is alternate. The pits found in the vessel element walls are similar in size to intervascular pits, while those found in the axial parenchyma walls are larger and simple. Ves- sel to ray parenchyma pitting is alternate and resem- bles the vessel to axial parenchyma pitting. Fibrous elements are nonseptate, having thin walls from 2 p to 5.u thick. The average length of the fibrous elements is 752p, with a range from 400p to 1150p and a MFR of 560p to 890p. Vascular rays are uniseriate to triseriate, some rays rarely 4 cells wide. The uniseriate rays range from 1 to 12 cells (150p) in height and are heterocellular. The biseriate and triseriate rays are up to 40 cells (500p) in height and are heterocellular, a few hav- ing uniseriate wings of from 1 to 4 cells high. In the case of both uniseriate and multiseriate rays, the great majority of cells are procumbent. Very few upright cells were seen in the material studied, ar- rangement of the cell types follows no pattern, and although the margins of the multiseriate rays may be a mixture of procumbent and square cells, the body of the ray comprises only procumbent cells. The ray cells in contact with vessel elements are frequent- ly disjunctive. Most ray cells contain starch grains. Axial parenchyma is present in both apotracheal and paratracheal arrangements. The apotracheal parenchyma is banded, diffuse, and diffuse-in-ag- gregates, some of which comprise crystalliferous strands of from 3 to 20 cells. The banded apotracheal parenchyma is made up of axially elongate paren- chyma strand cells, some of which have further sub- divided and are crystalliferous (crystalliferous strands). Many of the cells of the diffuse and dif- fuse-in-aggregates parenchyma are crystalliferous. The crystalliferous idioblasts are generally much en- larged, containing optically anisotropic prismatic NUMBER 5 13 crystals (Figure 25). The bands of axial parenchyma are from 1 to 4 cells wide and are continuous. Para- tracheal parenchyma is scanty vasicentric and some- times aliform. Axial parenchyma cells are frequently disjunctive. Most, if not all, of the axial parenchyma cells contain starch. The vessels often contain a granular to non- granular, translucent amorphous material aggregated on or near the perforation plates. Zanthoxylum fagara (L.) Sargent : Faint growth rings are present. Pores are circular, with walls rang- ing in thickness from 2p to 12p. Radial multiples are the predominant radially oriented pore group (Figure 14). Vessel element length averages 261p, with a range of 145p to 465p and a MFR of 210p to 310p. Ves- sel element end walls are inclined at an average of 64?. Vessel elements may be either ligulate or eligulate. Intervascular pitting comprises minute bordered pits ranging from 2p to 3p in diameter. Pit apertures are oval to lenticular and included within rounded borders. Vessel to axial parenchyma pitting and vessel to ray parenchyma pitting are similar in size, shape, and arrangement. The pit-pairs are half-bordered, with the bordered vessel element pits similar in size, shape, and arrangement to the intervascular bor- dered pits described above. The simple parenchyma pits (both axial and ray parenchyma) are generally circular to oval and are either approximately the same size as the bordered pits or large, elongate, and fenestriform. The imperforate tracheary elements are nonseptate, having walls which range in thickness from 2p to 6p and from thin to very thick (lumens entirely oc- cluded). The length of the fibrous elements averages 735p, with a range of 400p to 11 75p and a MFR of 600p to 1OOOp. Vascular rays are predominantly uniseriate and biseriate, with a few triseriate for at least a part of their length. All ray types are heterocellular. Uniseri- ate raps are frequently short, ranging in height from 2 to 6 cells or more, and are composed of either square or upright cells, or both. A second type of uniseriate ray is generally higher, ranging up to 10 cells or more in height, and consists of procumbent cells in addition to square and upright celIs, or both. The biseriate rays are generally higher than the uniseriates, ranging up to 400p (30 cells) or more in height, the biseriate portion of the ray is typically composed of only procumbent cells, while the uniseri- ate margins or ?wings? are composed of 1 to 5 or more horizontal rows of square and upright cells, or both. Starch is not present in the ray cells, possibly because of the hydrofluoric acid treatment of the specimen (Stern 2625) prior to sectioning. Axial parenchyma is present in apotracheal and paratracheal arrangement. The apotracheal paren- chyma occurs as continuous bands, ranging from 2 to 7 or more cells in width, comprising strand paren- chyma. Generally there are two cells per strand, al- though in some cases, one or both of these cells has further subdivided several times, giving rise to short strands of crystalliferous idioblasts. Scanty diffuse parenchyma comprises the same cell type as described above. The paratracheal parenchyma is scanty vasi- centric. Irregular and continuous periclinal cavities occur throughout the xylem of Stern 2625 (Figures 26, 2 7 ) . These cavities are apparently traumatic in origin and contain an evenly staining, homogeneous, opaque to transparent substance. Many of the vessels contain a granular to nongranular (similar in appearance to the homogeneous material seen in the traumatic cavities described above) , translucent to transparent material. Zanthoxylum flavum Vahl: Growth rings are present. Pores are circular to somewhat angular, with the vessel element walls ranging in thickness from 2p to 7p. The bulk of the radially oriented pores are intergrades between radial multiples and chains in which at least some pores have flattened tangential walls. Vessel element length averages 575p, with a range of 300p to 750p and a MFR of 475p to 650p. Ves- sel element end walls are inclined at an average of 44?. The vessel elements are generally ligulate. Intervascular pitting comprises small bordered pits ranging in size from 4p to 6p in diameter. The pit apertures are oval to lenticular and are included within rounded to somewhat angular borders. Vessel to axial parenchyma pitting and vessel to ray parenchyma pitting is similar in size, shape, and arrangement. The pit-pairs are half-bordered and alternately arranged. The bordered pit of the vessel element wall coincides in size and shape with those of the intervascular pit-pairs. Simple pits of the paren- 14 SMITHSONIAN CONTRIBUTIONS TO BOTANY chyma wall are round to oval and frequently elon- gate, the latter fenestriform. The imperforate tracheary elements are nonseptate. having walls that vary in thickness from 2p to 5p and range from thin in early wood to thick and very thick in late wood. These walls are optically inactive and, as such, may indicate that the fibers are actually gelatinous. The average length of the fibrous ele- ments is 1125p, with a range of 735p to 1 4 2 8 ~ and a MFR of 945p to 1300p. Vascular rays are uniseriate to triseriate, with biseriate rays predominating. The uniseriate rays range from 1 to 7 or more cells high and most frequently comprise only square and upright cells, or both. Some procumbent cells are seen in the uniseriate rays. Bi- and triseriate rays are approxi- mately the same size, ranging from 5 cells to over 25 cells (600p) in height. In both the bi- and tri- seriate rays, the multiseriate portion of the ray com- prises procumbent cells, while the uniseriate ?wings? or margins frequently comprise only square and up- right cells or both. The rays are heterocellular, com- prising all three cell types. Ray cells contain massive amounts of starch and are frequently crystalliferous. Axial parenchyma is present in apotracheal and paratracheal arrangements. The apotracheal paren- chyma occurs as continuous bands, which are usually, but not necessarily, marginal. When clearly marginal, these bands are initial and are 1 to 2 cells in width. The bands comprise strand parenchyma, many of which, having further subdivided, contain nonenlarged, optically active crystals. Diffusely ar- ranged crystalliferous strands are infrequently seen. The paratracheal parenchyma is exceedingly scanty, not common to every vessel, and never completely vasicentric. All types of axial parenchyma contain massive amounts of starch. SAPINDACEAE Cardiospermum halicacabum L. : Faint growth rings are present. Pores are rounded to somewhat angular with walls varying in thickness from 4p to lop thick. Two distinct sizes of vessel elements are present in this species (Figure 35.) The smaller of the two sizes is generally angular and arranged in radial multiples. These vessel elements are ligulate and have end walls inclined at an average of 45? (the measurement of the end wall angles are made on macerated material) . These small vessel elements intergrade with vascular tracheids. The larger of the two sizes are rounded and are either solitary or arranged in clusters. The large vessel elements are either ligulate or eligulate, with nearly horizontal end walls. The average end all inclination of the combined vessel element types, as measured in tangential sec- tion, is 76?. The average vessel element length is 200p, with a range of 130p to 290p and a MFR of Intervascular pitting comprises small pits, rang- ing in size from 4p to 6p in diameter. Pit apertures are oval to lenticular. Pit borders are rounded. Vessel to axial parenchyma pitting and vessel to ray parenchyma pitting, when viewed in section, are similar in appearance. The pit-pairs in both types of pitting are half-bordered. Pits in the vessel ele- ment wall are similar in size, shape, and arrange- ment to intervascular pits. A study of macerations reveals that the simple pits of the ray parenchyma are frequently small and slitlike to oval, while those of the axial parenchyma are large, oval to elongate, and fenestriform. Imperforate tracheary elements are frequently septate, having walls from 2p to 4p thick, ranging from very thin to thick. The average fibrous element length is 533p, with a range of 350p to 800p and a MFR of 440p to 60011.. A study of macerations indicates that two distinct types of fibrous elements are present. One type is typically thick-walled, having attenuated ends and infrequent, thin, solitary septa. The second type of fibrous element is generally thin-walled, having truncate end walls. This second type is frequently septate. Septa are thick and range from 1 to 3 or more per cell. Pitting is similar in both types and each may contain starch. Vascular rays are uniseriate to multiseriate, some rays are 4 or more cells wide. The multiseriate rays frequently have uniseriate margins. The rays range in height from a few cells to over 40 cells (800p) . The ray tissue is heterocellular, comprising upright, square, and procumbent cell types. Upright and square cells are most frequent, while procumbent cells are relatively rare. The arrangement of cell types follows no discernible pattern. Two or more cell types are commonly found in any given hori- zontal row. Ray cells are often crystalliferous or 160p to 250p. NUMBER 5 15 contain starch. Some of the ray cells contain a dark- staining, transparent to opaque substance of un- known composition. Axial parenchyma is present in both apotracheal and paratracheal arrangement. Diffuse parenchyma usually comprises crystalliferous strands. Additional apotracheal parenchyma is present in the form of a discontinuous band that may have been traumatic in origin in my specimen. Cells in these apotracheal parenchyma bands are also frequently crystalliferous. The crystalliferous idioblasts are nonenlarged rec- tangular cells, each containing a single optically anisotropic prismatic crystal. They are arranged in short vertical strands of from 3 to 10 or more cells. The paratracheal parenchyma is generally scanty vasicentric, although a few cases of vasicentric are seen. Axial parenchyma cells are frequently disjunc- tive. Both types of axial parenchyma contain massive amounts of starch and may contain the dark-staining substance seen in ray cells. Cupania glabra Swartz: Growth rings are present but not distinct. The pores are rounded, having walls from 2p to 7p thick. Average vessel element length is 414p, with a range from 65p to 610p and a MFR from 340p to 500p. Vessel element end walls are inclined at an average of 44'. The vessel elements are gen- erally ligulate. Intervascular pitting comprises minute bordered pits which range from 2p to 4p in diameter. Pit borders are rounded; pit apertures are rounded to elliptical and are included within the borders. Vessel to axial parenchyma pitting is alternate to scattered. Many of the pits in the parenchyma cell walls are large, simple, and fenestriform with ir- regularly shaped margins. The pits in the vessel walls are slightly to completely bordered. Vessel to ray parenchyma pitting is the same as that described for vessel to axial parenchyma pitting. The imperforate tracheary elements are septate. Most of the fibrous elements contain 2 or more septa. The cell walls are 2p to 5p thick and are thin as compared with the diameter of the lumen. The average length of the fibrous elements is 697p, with a range of 375p to 950p and a MFR of 630p to 840p. Vascular rays are, for all intents and purposes, uniseriate. A few rays possess biseriate segments but these are localized and never extend the length of a ray. The rays may be up to 20 cells (300p) or more in height, but generally range from 4 to 10 cells high. Rays are heterocellular, comprising mainly procumbent and square cells, with upright cells oc- curring infrequently. There is no pattern of arrange- ment of cell types, although the procumbent cell type makes up the bulk of most rays, while the square cell type frequently occurs in marginal rows. Both square and procumbent cells occur in the same hor- izontal row. Most of the ray cells contain a dark- staining, transparent to opaque substance of unknown composition. Axial parenchyma is present in both apotracheal and paratracheal arrangements. Apotracheal paren- chyma is mainly diffusely arranged, crystalliferous strand parenchyma. There is continuously banded apotracheal parenchyma 1 to 3 cells wide. The diffuse crystalliferous strands are of frequent occurrence, and range up to 30 cells or more in height. Strand cells, when viewed in longitudinal section, are rectangular, with most of the cells in a given strand being crystalliferous. Apotracheal bands comprise primarily crystalliferous strand parenchyma, but unlike the diffuse strands, the cells of the bands contain the same dark-staining substance seen in the ray cells. The paratracheal parenchyma is scanty vasicentric and frequently contains the same dark- staining substance previously mentioned, Dodonaea viscosa (L.) Jacquin: Growth rings are absent. Pores are circular with walls varying in thickness from 3p to 7p. Vessel element length averages 234p, with a range of 120p to 330p and a MFR of 200p to 270p. Vessel element end walls are inclined at an average of 54'. Vessel elements are either ligulate or eligulate. Intervascular pitting comprises minute bordered pits ranging from 2p to 4p in diameter. Pit borders are rounded; pit apertures are lenticular and slightly extended beyond or included within the borders. Vessel to axial parenchyma pitting and vessel to ray parenchyma pitting are very similar and both fit the following description. The arrangement of pits in the vessel wall is alternate. Vessel to paren- chyma (both types) pit-pairs are half-bordered; the bordered pit of the vessel wall coincides in size and shape to the intervascular pits, while the simple pits of the parenchyma wall are generally irregularly shaped, ranging from circular to elongate, and are frequently fenestriform. 16 SMITHSONIAN CONTRIBUTIONS TO BOTANY Imperforate tracheary elements are nonseptate, having a wall thickness from 3p to 7p which ranges from thick to very thick, the lumens of some cells entirely occluded. The average length of the fibrous elements is 525p, with a range of 250p to 720,~ and a MFR of 440p to 650p. Vascular rays are predominantly uniseriate. Some biseriates are present, either as short biseriate seg- ments in otherwise uniseriate rays or as completely biseriate rays. The rays are heterocellular, comprising procumbent and square cells. Very few upright cells are seen. There is no discernible pattern of cell ar- rangement and both square and procumbent cell types frequently occur in the same horizontal row. There is a tendency, however, for the main body of a given ray to be composed primarily of procumbent cells. The occurrence of the square cells is sporadic in all cases, their arrangement random. Uniseriate rays range in height from 2 to 20 cells (300p) or more, while the biseriates generally range from 5 to 15 cells in height. The ray cells frequently contain a dark-staining, transparent to opaque sub- stance of unknown composition. Axial parenchyma is present in both apotracheal and paratracheal arrangement. Apotracheal paren- chyma is primarily diffuse, consisting mainly of crystalliferous strands. Some continuously banded parenchyma occurs, these bands ranging in width from 1 to 3 or more cells. The diffuse crystalliferous strands are generally short, usually 10 or fewer cells per strand, and composed of slightly enlarged idio- blasts, each containing a single optically anisotropic prismatic crystal. The paratracheal parenchyma ranges from scanty vasicentric to aliform, with in- frequent confluent banding occurring. This banding is local (not continuous) and is definitely associated with the vessel elements. Axial parenchyma fre- quently contains the dark-staining material seen in the ray cells. Exothea paniculata (Jussieu) Radlkofer: Growth rings are present. Pores are rounded; the walls are from 2p to 8p thick. Vessel element length averages 428p, and ranges from 245p to 560p, with a.MFR of 400p to 500p. Vessel element end walls are inclined at an average of 43 O , Vessel elements are generally ligulate. Intervascular pitting comprises minute bordered pits, ranging from 2p to 3p in diameter. Pit borders are circular; pit apertures are lenticular and extend beyond the pit borders. Vessel to ray parenchyma pitting and vessel to axial parenchyma pitting are very similar in appear- ance. In both cases, the arrangement of pits in the vessel wall is alternate and the pits are similar in size and shape to intervascular pits. The vessel to parenchyma pit-pairs (both types of parenchyma) are half-bordered, with the simple pits of the paren- chyma wall ranging from circular to elongate, and fenestriform. The imperforate tracheary elements are septate, most having two or more septa per cell. The cell walls are 2p to 5 , thick, and range from thin in early wood to very thick in late wood. The average length of the fibrous elements is 716p, and the range is 440p to 1010p with a MFR of 630p to 800p. The fibrous elements often contain starch. Vascular rays are uniseriate and biseriate, the latter type predominating. Uniseriate rays are gen- erally low, most are from 2 to 5 cells high. The bi- seriate rays are somewhat higher, generally ranging from 8 to 15 cells (250p). Upright cells are rare. Ar- rangement of these cell types follows no pattern; both procumbent and square cells occur in the same horizontal rows. Procumbent cells predominate and comprise the bulk of most rays. Most ray cells con- tain a dark-staining, transparent to opaque sub- stance of unknown composition in addition to starch. Axial parenchyma is present in both apotracheal and paratracheal arrangement. Apotracheal paren- chyma is present in diffuse crystalliferous strands and as banded and marginal parenchyma. The crystalli- ferous strands are of frequent occurrence and range up to 20 cells or more in height. Crystalliferous idio- blasts do not appear to be enlarged and each gen- erally contains a single prismatic crystal. Bands of parenchyma may be up to 5 cells wide and are com- posed of both crystalliferous and noncrystalliferous strands. The bands may or may not be marginal and are unevenly spaced. The arrangement of the para- tracheal parenchyma ranges from scanty vasicentric to vasicentric. All types of axial parenchyma cells frequently con- tain starch and the dark-staining substance seen in the ray cells. This dark-staining substance may also occur in the vessels. Hypelate trifoliata Swartz: Faint growth rings are present. Pores are rounded, with walls varying in thickness from 3p to 7p. NUMBER 5 17 Vessel element length averages 319p, with a range of 200p to 515p and a MFR of 275p to 400p. Vessel element end walls are inclined at an average of 47'. The vessel elements are generally ligulate. Intervascular pitting comprises minute pits rang- ing from 2p to 4p in diameter. Pit apertures are rounded to oval and included within rounded to polygonal borders. Vessel to axial parenchyma pitting and vessel to ray parenchyma pitting are similar in appearance. Both are alternate to scattered in arrangement and half-bordered, the pits in the vessel walls are similar in size and shape to the intervascular pits. The imperforate tracheary elements are non- septate, having walls which vary in thickness from 3p to 7p and range from thick to very thick, the lumens of some cells entirely occluded. The average length of the fibrous elements is 632p, with a range of 420p to 850p and a MFR of 525p to 780p. Vascular rays are uniseriate. The rays are hetero- cellular, comprising procumbent, square, and up- right cells. The main body of most rays is composed of square and procumbent cells, both frequently oc- curring in the same horizontal row. Upright cells are generally found in the marginal rows. The rays range in height from 2 to 25 cells (350p) or more, most rays are 10 or fewer cells high. Axial parenchyma is present in both apotracheal and paratracheal arrangement. Apotracheal paren- chyma is diffuse and comprises crystalliferous and noncrystalliferous strands. The crystalliferous strands range from 4 to 30 cells or more per strand, com- prising square idioblasts, each containing a single prismatic crystal. Paratracheal parenchyma ranges from vasicentric to aliform, with some confluent present. A few of the paratracheal parenchyma strands contain crystalliferous cells. Sapindus saponaria Linneaus : Growth rings are absent. The pores are circular and have walls from 2p to 5p thick. Vessel element length averages 278p, with a range of 120p to 390p and a MFR of 220p to 330p. End walls are inclined at an average angle of 62'. In general, the vessel elements are ligulate. Intervascular pitting consists of minute pits, rang- ing from 3p to 4 p in diameter. The pit apertures are oval to lenticular and included within rounded to somewhat angular borders. Vessel to both axial and ray parenchyma pitting is alternate and half-bordered in nature. The bordered to slightly bordered pits in the vessel walls are very similar in size and shape to intervascular pits, while the pits in the parenchyma walls are large and simple. Imperforate tracheary elements are septate, gen- erally having a single thin septum in each cell. Walls vary in thickness from 2p to 4p and are thin in com- parison with the dimensions of the lumens. The aver- age length of fibrous elements is 911p, with a range of 650p to 1180p and a MFR of 800p to 1100p. Vascular rays are uni- to triseriate, with biseriate and triseriate rays predominating. Rays are homocel- lular, comprising only procumbent cells. The uni- seriate rays are generally short, from 2 to 10 or more cells high. A few of the uniseriate rays, when seen in tangential section, appear to be made up of some enlarged square type cells. However, examination of radial sections showed that, although some cells were higher than other cells, they were nevertheless radi- ally elongate and thus procumbent. The biseriate and triseriate rays are generally higher than the uni- seriates, ranging up to 50 cells (400p) or more in height. Infrequently, enlarged marginal cells are in the bi- and triseriate rays, but examination of radial sections shows that these cells, although somewhat larger, are still radially elongate. All of the rays fre- quently contain large amounts of starch (starch grains). Axial parenchyma is abundant and confluent. Whether this situation represents true confluent, that is, paratracheal, parenchyma is difficult to determine, for the bands of axial parenchyma are frequently so wide as to occupy a large proportion of the ground- mass (Figure 18). These numerous, wide bands thus surround most of the vessels (pores). I t would be impossible, without ontogenic studies, to say whether this is fortuitous. The bands comprise two types of strand parenchyma: strands of 2 to 4 axially elongate cells, and strands of many cells, a large number of these crystalliferous. The largely crystalliferous strand parenchyma is commonly found at the margins of the parenchyma bands. These strands were not seen distributed among the fibrous elements. The crystal- liferous idioblasts are not enlarged. Distinctly vasi- centric parenchyma is also seen in which cells are typically flattened and frequently disjunctive, form- ing a complete sheath around each vessel or group of vessels. These cells are distinct from the remainder 18 SMITHSONIAN CONTRIBUTIONS TO BOTANY of the axial parenchyma because they contain the same darkly stained substance found in the vessels. Starch grains often occur in cells of the banded parenchyma, but not in cells of vasicentric paren- chyma. SIMAROUBACEAE Simarouba glauca DeCandolle : Growth rings are absent. Pores are circular, with walls from 3p to 12p thick. Vessel element length averages 446p, with a range of 270p to 560p and a MFR of 400p to 500p. Vessel element end walls are inclined at an average of 60?. Vessel elements are generally eligulate. Intervascular pitting comprises small bordered pits, ranging in size from 5p to 7 p in diameter. Pit apertures are oval and included within rounded to somewhat angular borders. Vessel to axial parenchyma pitting and vessel to ray parenchyma pitting is similar in size, shape, and arrangement. The pit-pairs are half-bordered, the bordered pits of the vessel wall alternate and similar in size to the intervascular pits. The simple pits of the parenchyma are round to elongate, frequently fenestriform. Imperforate tracheary elements are nonseptate, having walls which range in thickness from 1p to 3p and vary from thin to very thin. The average length of the fibrous elements is 794p, with a range of 550p to 111Op and a MFR of 650p to 950p. Vascular rays are uniseriate to multiseriate, with biseriate and triseriate rays predominating. Infre- quently, the rays are up to five cells wide. All of the rays are similar in size, although the uniseriates are generally shorter than the bi- and triseriates. The uniseriate rays range from 4 to 10 cells or more high. The bi- and triseriate rays range from 5 to 30 cells (400p) or more high. Rays are heterocellular, al- though composed almost entirely of procumbent cells: square cells are seen, but are infrequent in occurrence and random in arrangement. The rays cells frequently contain starch. Rays are storied (Figure 23). Axial parenchyma is present in paratracheal ar- rangement as narrow, anastomosing confluent bands. The bands are frequently continuous and range from 3 to 10 cells or more wide. Some of the bands are discontinuous and, as such, constitute an aliform con- figuration with long ?wings.? Axial parenchyma com- prises strands generally consisting of four cells each. The strands tend to be storied. (Figure 23). Crystal- liferous strand parenchyma is also present, each strand consisting of 5 to 10 or more cells. The crystalliferous idioblasts are rectangular, nonenlarged cells, each containing a single optically anisotropic prismatic crystal. Axial parenchyma cells that are in contact with vessel elements are generally flattened and frequently disjunctive. Cells in strand paren- chyma frequently contain starch. Suriana maritima Linnaeus: Growth rings are ab- sent. Pores are circular, with vessel element walls ranging in thickness from 2p to 6p. Vessel element length averages 173p, with a range of 45p to 230p and a MFR of 165p to 200p. Vessel elements are generally eligulate. Intervascular pitting comprises minute bordered pits ranging in size from 3p to 4p in diameter. Pit apertures are lenticular to oval and are included within or are extended slightly beyond the rounded to somewhat angular borders. Vessel to axial parenchyma pitting and vessel to ray parenchyma pitting are similar in size, shape, and arrangement. The pit-pairs are half-bordered and alternately arranged. The bordered pits of the vessel elements are similar to intervascular pits, while the simple pits of the parenchyma (both ray and axial) are frequently large, oval to elongate, and fenestriform. Imperforate tracheary elements are nonseptate, having walls which vary in thickness from 2p to 6p and range from thin to thick. Some of the fibrous elements in Stern @ Briticky 230 are gelatinous and in Stern @ Brizicky 230 and Stern 2666 they contain a darkly staining, translucent to opaque substance of unknown composition. The average length of the fibrous elements is 586p, with a range of 335p to 780p and a MFR of 460p to 700p. Vascular rays are uni- and biseriate, with the uniseriate rays predominating. Rays make up a large portion of the groundmass as viewed in longitudinal section. Rays are heterocellular, comprising mainly upright and square cell types, the procumbent cell type occurs infrequently. Arrangement of the various cell types is random. Both the uniseriate and the biseriate rays are short, generally ranging from 3 to 15 cells or more in height. All of the ray cells con- NUMBER 5 19 tain the dark-staining substance found in the fibrous elements. Axial parenchyma is present in both apotracheal and paratracheal arrangement. Apotracheal paren- chyma is diffuse and diffuse-in-aggregates and com- prises noncrystalliferous strands consisting of two cells or more per strand. The paratracheal parenchyma is scanty vasicentric to vasicentric, and frequently comprises disjunctive cells. Both types of axial pa- renchyma cells contain the same dark-staining sub- stance present in the fibrous elements and the ray cells. An anastomosing arrangement of cells con- taining this substance is seen in transverse section and comprises primarily the diffuse-in-aggregates apotracheal parenchyma and rays. Vessel elements frequently contain either this dark- staining amorphous substance, or a granular sub- stance, which is similarly stained. Those vessel ele- ments with empty lumens frequently have their cell walls coated with this dark-staining substance. Discussion Since structures which tend to be easily modified in response to environmental changes are of relatively little taxonomic importance, the choice of characters to be studied is critical. In this respect, the compo- nents of mature secondary xylem tissue are consid- ered relatively implastic, especially when compared with characters of external morphology (Metcalfe and Chalk 1950). Of the large number of anatomi- cal characters discernible from study of mature sec- ondary xylem, however, certain characters appear to be more plastic than others. Characters incor- porating dimensions are, in general, more apt to vary with change in environment and growing con- ditions. The presence or absence of growth rings, the lengths of fibrous elements, and the number of vessels per unit area are examples of plastic characteristics which are usually of little taxonomic significance. On the other hand, characters of form or arrangement are often less plastic and therefore more significant taxonomically. As examples of these, one may cite the arrangement of intervascular pitting, the organi- zation of axial parenchyma, and the configuration of perforation plates. In addition to the relatively implastic nature of the anatomical characters of wood, the structure of wood tends to be evolutionarily more conservative than features of external morphology (Metcalfe and Chalk 1950). As a result, differences in the wood structure are inclined to be less dramatic than are differences in external morphology. Thus, Metcalfe and Chalk state that ". . . this [the implastic nature of wood structure], combined with its more conserva- tive nature, adds to its value for the study of larger groups." In addition to being taxonomically valuable as a basis of classification, anatomical variations in sec- ondary xylem may reflect the phylogenetic status of plant taxa. Although vessel element length may vary greatly within different plants of the same species and even within the tissues of the same plant, de- pending upon the age and position of the tissue studied (Bailey and Tupper 19 18), vessel element length is the most accurate reflection of the fusifom cambial initial length (Chalk and Chattaway 1934). Bailey and Tupper correlated fusiform cambial initial length, as reflected by the length of vascular ele- ments, with degree of evolutionary development based on both fossil and extant plants. They found that Calamitales, Lepidodendrales, and Cycadofili- cales, in addition to extant vascular cryptogams, possessed the longest tracheary elements ; gymno- sperms, both extant and extinct, possessed tracheary elements of intermediate length; and extant dicots had the shortest vascular elements. From this classic work, based on a large number of plants of wide distribution within the extinct and extant tracheo- phytes, one is led to conclude that a reduction in lengh of fusiform cambial initials is associated with evolutionary advance (specialization) . Frost ( 1930a, 1930b, 1931 ) , Bailey and Tupper (1918), Kribs (1935, 1937), and others correlated the lengths of the fusiform cambial initials with other features of dicotyledonous xylem anatomy. They con- cluded that definite trends of specialization accom- panied the evolutionary reduction in length of the fusiform cambial initials. Thus, the systematist, if he so chooses, has at hand a tool of great potential taxonomic importance. Us- ing characters derived from the study of wood anat- omy as correlative and complementary information, he has an independent means of testing presumptive phylogenetic relationships. These means are not based on the circuitous reasoning commonly en- countered in classification based only on morpholog- ical characters, e.g., a plant is considered primitive SMITHSONIAN CONTRIBUTIONS TO BOTANY because it possesses a primitive flower type, which itself is considered primitive because it is character- istic of a ?primitive? taxon. The seemingly unrelated characters of perforation type, end wall inclination, intervascular pitting, etc., are now recognized as constituting a syndrome or correlative complex use- ful in reflecting not only form relationship, but the evolutionary status of the plant. As Bailey (1957) stated, ?The chief trends of evolutionary specializa- tion in the cambium and xylem of dicotyledons are now so reliably established (except in the case of certain patterns of wood parenchyma distribution) that they can be utilized to advantage in studying salient problems of phylogeny and classification.? A final point must be made on the value of xylem anatomy in the overall scope of classification. In it- self, xylem anatomy is of little inherent value to the taxonomists. Bailey (1953) stated that wood struc- ture, as a collection of internal or endomorphic characters, is ?. . . inherently no more conservative or reliable than are exomorphic ones.?? Any given structure or character is not universally plastic or implastic; a character which may be implastic and thus of taxonomic value within one group of plants, may be quite variable and thus of little use in another. Thus, endomorphic xylem characters of and by themselves, are of no more intrinsic value to the taxonomist than are exomorphic characters. However, when used in conjunction with other data derived from external morphology, in addition to other areas of study, xylem anatomy can be of sig- nificant value. When utilized by itself, xylem anat- omy best serves the taxonomist as a means of nega- tion of relatedness among taxa (Bailey 1957, Cron- quist 1968). Because of the ever-present possibility that similar structures may result through parallel evolution, xylem characters alone cannot be con- sidered as indicative of positive relationship without the strong support of supplemental data. A brief comparison of the anatomical features of the taxa included in this study follows. In general, these anatomical features conform well with those previously reported in the literature. Some discrep- ancies are indicated below. The single observation of an apparent multiple perforation plate in Metopium toxiferum is unique in that all other perforations observed in this study are simple. Although at least two genera of Ana- cardiaceae are reported in the literature (Metcalfe and Chalk 1950, Heimsch 1942) as having multiple perforations in addition to simple perforations ( Campnosperma and Heeria) , Metopium is reported as possessing only simple perforations (Heimsch 1940). If the perforation observed is indeed a mul- tiple perforation and not a collection of fenestriform vessel to parenchyma pits clustered at the end of the vessel (as suggested in the description), the occur- rence of such multiple perforations is extremely in- frequent. Either interpretation leads one to conclude that, for all intents and purposes, the xylem of Metopium is characterized by simple perforations. My observation that Toxicodendron radicans has diffuse-porous wood raises some questions. The genus Toxicodendron is reported (Heimsch 1942, Metca?fe and Chalk 1950, Record and Hess 1943) as having generally ring-porous wood. Is the diffuse-porous wood of Stern 2633 (Figure 19) a result of environ- mental factors, or is it simply a feature of immature tissue? As noted in the description, the outer growth rings exhibit a tendency toward ring porosity. On the Florida Keys, T . radicans never has stems that even approach the robust stems of this species growing in northeastern United States. I t is possible that the de- pauperate growth of the stem on the Keys may have some bearing on the formation of ring porosity. The climate of the Keys is probably conducive for p!ant growth throughout the year. This in itself will have an influence on the formation of growth rings and may seriously affect the expression of typical ring po- rosity in this species as it occurs on these islands. Spiral thickenings are not present in the vessel ele- ments of T . radicans, although all memberss of the genus Toxicodendron are reported (Record 1939) as having this feature. Heimsch (1940) reports the presence of spiral thickenings in the small vessel elements of only T . uernix and the Asiatic T . tricho- carpum. Heimsch notes, as a possible explanation of this discrepancy, that the portions of the vessel element wall occurring between the slitlike inter- vascular pits and the fenestriform vessel to paren- chyma pits give the impression of spiral thickenings in unstained or poorly stained sections. My observa- tions agree with those of Heimsch to the extent that no spiral thickenings were seen in the specimen of T . radicans. * Record?s description of the wood characters of the genus Toxicodendron is based on specimens of T . diversiloba, T . radicans, and T . vernix. NUMBER 5 21 Striking similarities occur among Metopium toxi- ferum, Toxicodendron radicans, and Bursera sima- ruba. These s;ecies have fenestriform vessel to pa- renchyma pit-pairs (Figure 32). Metopium toxiferum and Bursera simaruba have medium-sized (in diam- eter) intervascular pitting. Other species of Pinnatae studied have vessel to parenchyma pitting which is very similar structurally to the intervascular pitting, the intervascular pits ranging in size from small to minute in diameter. Metopium toxiferum and Bursera simaruba have horizontal intercellular canals in their rays (Figure 24). Record (1939) notes that these canals occur in Toxicodendron diversiloba, although Heimsch (1940) did not observe radial canals in any members of the genus. Rays in Meto- pium toxiferum, Bursera simaruba, Swietenia ma- hagoni, and the two species of Zanthoxylum are so similar as to be hardly distinguishable, except for the occurrence of intercellular canals. Field collection of the two species of Zanthoxylum points up an obvious difference between Z. fagara and Z. flavum. Although Z. flavum is reported in the literature as possessing wood (heartwood) which is ". . . exceedingly hard and heavy" (Small 1933), having ". . . sp. gr. .90, 56 Ibs./cu. ft." (Record and Hess 1943), hand sawing showed that, of the two species, Z. fagara was much harder. Upon study of the sections of Z. flavum, I was surprised to note the presence of thick-walled fibers and a small amount of axial parenchyma (as compared with Z. fagara, Figures 14, 15) , certainly not what one would expect of the very soft wood Z. flavum proved to be on sawing. Observation of transverse sections under crossed nicols reveals, however, that the sec- ondary wall thickenings of the fibrous elements of Z. flavum are optically inactive, while those of Z. fagara are optically active. This indicated that, although the secondary walls of the fibrous elements of Z. flavum are lignified (take up safranin stain readily), the orientation of the cellulose micelles of these secondary walls is such that polarized light is not refracted in the transverse plane of section. Although not typical in appearance, one could refer to these fibrous elements as gelatinous, owing to the apparent noncrystalline nature of the secondary wall thickenings. The wide occurrence of gelatinous fibers could explain the softness of the wood in Z. flavum. A character which separates members of the Ru- taceae from the other Pinnatae is the presence in the rutaceous taxa of at least some radial chain pore arrangement (Figure 15). In other Pinnatae, the radially oriented pore groups comprised only radial multiples (Figure 12). All members of the Rutaceae have banded and diffuse axial parenchyma in addi- tion to some paratracheal parenchyma. Swietenia mahagoni, Metopium toxiferum, and several mem- bers of the Sapindaceae also have this combination of axial parenchyma arrangements. Amyris and Citrus have enlarged crystalliferous idioblasts (Figure 25), as does Dodonaea of the Sapindaceae. The occur- rence of crystals in either ray parenchyma or axial parenchyma is a nearly universal character of the species studied. Only Metopium toxiferum, Toxico- dendron radicans, and Suriana maritima lack such crystals. Although the xylem anatomy of Cardiospermum halicacabum is not described in the literature (Heimsch 1942, Metcalfe and Chalk 1950, Record and Hess 1943), the xylem of two genera (Serjania and Paullinia) of sapindaceous lianas are described. The occurrence of two distinct vessel element types in Cardiospermum (Figure 35) noted above con- forms with the descriptions of vessel elements given for Serjania and Paullinia (Heimsch 1942, Metcalfe and Chalk 1950). The presence of dimorphic vessel elements is likely related to the lianous habit in this family. Throughout this investigation, various anatomical characteristics were evaluated, with the hope that1 a significant set of these could be found which might reflect the present familial arrangement of the 16 species studied. Although certain families did possess anatomical features which served to identify their members, other families did not possess such unify- ing features. However, all the members of Pinnatae do exhibit many anatomical characters in common to indicate that we are dealing with a remarkably homogeneous group of plants. Comparison among families of Pinnatae of those anatomical characters considered to be of greatest taxonomic and phylogenetic significance by Metcalfe and Chalk (1950) reveals that (1) all members possess vessel elements having simple perforations, ( 2 ) the vessel elements of all members have alter- nately arranged intervascular pitting, (3) all mem- bers possess fibers with slitlike simple to slightly bordered pits, and (4) all members possess at least paratracheal axial parenchyma, with the banded 22 SMITHSONIAN CONTRIBUTIONS TO BOTANY configuration (paratracheal and apotracheal) the most common. Although anatomical differences exist among the 16 species studied, none of these is great enough to warrant the exclusion of any one of the members from this group. By and large, greater anatomical differences are seen to exist among gen- era within the same family (e.g., Sapindaceae- Table 4) and even among species of the same genus (e.g., Zanthoxylum-Table 4) , than exist among the families represented in this group. Although the ray structure encountered in this study varies in regard to cellular makeup (hetero- cellular as opposed to homocellular, uniseriate as opposed to multiseriate) , the relative sizes of the rays of each species are similar. The rays of species having only uniseriates are low, rarely exceeding 2OOp in height. Those rays in species having multi- seriates are also low, rarely exceeding 600p in height. The widest multiseriate rays do not exceed 10 cells ( l o o p ) in width. Looking at anatomical characters which vary within the group as a whole, but remain relatively constant at the family level, we find an interesting and significant segregation. The nature of the vessel to parenchyma (both axial and ray) pitting is re- markably consistent among the 15 genera, with the three exceptions of Bursera, Metopium, and Toxico- dendron. Only Bursera and Metopium of the 15 TABLE 4.-Summary of xylem anatomical data in the "Pinnatae" SPECILS ANACAFDIACEAE Metapiir. toxife?wi Toxicade?.dron radicans BURSEFACEAE B ~ r s e r a sisaruba __- TZLIACFAE Swietenia mhegoni RUTACEAE Amyris elernifera Citm6 a u r a n t i i f o l i a Zanthaxyllun 2. fl8"Ul SApINDACEbi _ - Cardiospemm h a l i c e s a b m Cupacia glabra Jkdanaea viscose ~ _ _ panim1ata m e l a t e trifoliata Sepindus sapoIia?ia SDNLROUBACEAE S i m m u b a glauca Suriana mar i t ima -- 42 4 u ri y 1 1 > .5 L, 4: ;2 - 375 253 531 '137 25c 273 261 515 200 414 234 426 319 278 446 173 - - ELEK - ci J u r i a OJri m a c Loo m a G I - > d 2: ? $ m a - 4ir 41 48 62 55 58 64 44 76 44 54 43 '17 62 6c 63 - - S i ri a n" 42 3 . 4 5 :% u r N i .i 0 ) - - medim Small rnediwr. nin-te s i n u t e srnE.11 minute small small minute minure minute minute m.ir.use small minute B, A l , C D, s, v S B, #, S , ' J C, A1 D, s, v 1 , 2 , 1 , ~ het 1, horn. L,3,ZnL, het L 3 3 , h e t . 1 , 3 3 , h e t . 'Classification of intervascular p i t t i n g fo l lows t h a t swges ted by Record snd Chattaway (19?9). bUnderlined nurr.bers indicate t h e predominant ray type (2 = t P i E e r i s t e rays most freqilent ). *Xembers having Septate f ibrous elements which c o n t a i n s tarch. NUMBER 5 23 genera possess intervascular pits of medium size, the other 13 genera have either small or minute pits. Four genera possess heterocellular multiseriate rays having uniseriate wings, and among them are Bur- sera and Metopium. Add to this the horizontal inter- cellular canals in the rays of both Bursera and Meto- pium, and one recognizes that the members of the Florida Keys Pinnatae may be subdivided on the basis of xylem anatomy so that the genera of Ana- cardiaceae and Burseraceae are by and large dis- tinguishable from the other genera. Phylogenetic interpretation of the data derived from this study indicates that the woods of the 16 species exhibit a high degree of specialization. The syndrome of short to medium length vessel elements, simple perforation plates, alternate intervascular pit- ting, and absence of steeply inclined vessel element end walls shows that the members of the Pinnatae studied are at approximately the same relatively advanced level of specialization. In addition, the storied structure, found in Simarouba and Swietenin (Figure 23), represents another line of specialization which occurs only in certain Pinnatae. Kribs (1935) considered woods having either homocellular rays (Amyris and Sapindus) or strictly uniseriate rays (Amyris, Cupania, and Hypelate) as highly ad- vanced. The rays of Suriana are, for all intents and purposes, uniseriate. Heterocellular rays which are made up in large part of procumbent cells, with the square and upright cells, or both, occurring only sporadically and infrequently (Citrus and Sima- rouba) , are also considered as relatively advanced. The common ray configuration (procumbent cells comprising the multiseriate portion with upright' and square uniseriate wings or both) seen in Meto- pium, Bursera, Swietenia, and Zanthoxylum, in ad- dition to the low rays found in the remainder of the genera, constitutes an advanced ray situation. The presence of various aggregate arrangements of axial parenchyma, such as banded, aliform and confluent, or both (only Toxicodendron, Bursera, and Suriana lack such arrangements), is accepted as being advanced. The occurrence of fibrous ele- ments lacking distinctly bordered pits is also an advanced characteristic. The wide occurrence of starch grains in the par- enchymatous tissue of the specimens studied prob- ably is of little taxonomic significance. However, specimens of Toxicodendron, Bursera, Exothea, and Cardiospermum have septate fibrous elements that contain this storage product (Figures 12,13,24,29) . This feature may be of some taxonomic import in that it is correlated with a relatively small amount of axial parenchyma in these taxa. This observation is in agreement with those of Harrar ( 1946). The occurrence of septate fibrous elements appears to be a local phenomenon and is of little taxonomic significance in this group (the Pinnatae) . The only families that have members lacking septate fibers, based on the species in this study, are Rutaceae and Simaroubaceae. Both of these families, however, have other members that have septate fibers (Metcalfe and Chalk 1950). The taxonomic value of diffuse-porosity is also questionable, The effect of environment on the topography of wood is not certain. The great ma- jority of tropical trees having distinct growth rings possess woods that are diffuse-porous, and the OC- currence of ring-porosity is largely restricted to woody plants of the North Temporate Zone (Gilbert 1940). The fact that all members, with the possible excep-, tion of Toxicodendron, have diffuse-porous wood is thus of debatable taxonomic value here. A survey of the literature (Metcalfe and Chalk 1950), concerning both morphological and anatomi- cal characteristics of the families concerned with in this study, shows that the occurrence of secretory structures (Figures 24-27) characterizes members of the Pinnatae. The intercellular canals of anacar- diaceous and burseraceous woods, and the inter- cellular canals in the bark and pith of these families, as well as Simaroubaceae and Sapindaceae, are examples of such structures. Secretory cells are re- ported as occurring in the pith and cortex of all families. The occurrence of pellucid glands in the leaves of Rutaceae is well known. In addition, trau- matic axial canals are reported to occur either fre- quently or sporadically in some members of all fam- ilies, with the exception of Sapindaceae and Ana- cardiaceae. The widespread presence of dark-stain- ing, gumlike substances in the parenchyma and vessels of many of the species seen in -this study (Figures 20,22) suggests the secretory potential of these members. The traumatic axial canal observed in Zanthoxylum fagara also contained a darkly stain- ing deposit. Crystals, which occur widely in the xylem of Pinnatae are products of idioblasts. These too are considered as secretory cells. Thus, the oc- SMITHSONIAN CONTRIBUTIONS TO BOTANY currence of secretory structures in most, if not all members, may be of taxonomic value; insofar as it might serve as another indication of the homogeneous nature of Pinnatae. The data derived from this study indicate that the Pinnatae constitute a homogeneous group, and that no anatomical basis exists for segregation of the various members into separate orders. The traditional Englerian separation of the Sapindaceae and Ana- cardiaceae from the remainder of the families is not supported by xylem anatomy. Hutchinson?s separa- tion of the families into three orders, and Takhta- jan?s and Thorne?s separation of Sapindaceae from the other families, likewise, have no anatomical basis. Cronquist?s treatment most nearly reflects the ana- tomical similarities that exist, with the exception that he removes Suriana from the Simaroubaceae and places it into the Stylobasiaceae. There is no anatomical foundation for the separation of Suriana from the Simaroubaceae. This conclusion is based both on data derived from this study and the ana- tomical literature (Webber 1936). Cronquist?s (1968) assignment of Suriana and Stylobasium to his Stylo- basiaceae is based on characters of habit and mor- phology, and a complete study of the anatomy of Stylobasium and Suriana must be carried out before such an association can be anatomically evaluated. The inclusion of Anacardiaceae and Burseraceae in the single family Terebinthaceae, as proposed by Hallier (1912), is supported by xylem anatomy. Summary A study of the wood of 16 species of Florida Keys Pinnatae indicates that the group is anatomically homogeneous. All members possess simple perfora- tion plates, vessel elements having alternate inter- vascular pitting, fibrous elements with small slitlike, simple to vestigially bordered pits, and axial pa- renchyma which is both apo- and paratracheal. Crystals are of wide occurrence in the parenchyma cells, and banded and aliform to confluent paren- chyma occur in several taxa. Certain families or groups of families have unique characters : radial chain arrangement of pores in the Rutaceae, random arrangement of cells in the heterocellular ray types among members of the Sapindaceae, and fenestriform vessel to parenchyma pit-pairs and intercellular ca- nals in the rays of Anacardiaceae and Burseraceae. The only separation of families within Pinnatae suggested by a syndrome of several unique charac- teristics is the formation of an Anacardiaceae-Bur- seraceae complex. These characteristics, however, when viewed in light of the many common features of the families, are not sufficient bases for the sepa- ration of the Anacardiaceae and Burseraceae from the Pinnatae as a group. There is no anatomical basis for the separation of families into distinct orders as proposed by Engler, Hutchinson, Takhtajan, and others. The system of classification proposed by Cronquist is anatomically feasible except for his exclusion of Suriana from the Simaroubaceae. The members of the Pinnatae are seen by this author as belonging to a taxon corre- sponding well with Cronquist?s Sapindales. Phylogenetically, the Pinnatae constitutes an ad- vanced taxon. Simple perforation plates, short to medium length vessel elements having alternate in- tervascular pitting, slightly inclined vessel element end walls, advanced ray types, fibrous elements with simple or vestigially bordered pits, and the predomi- nant banded and confluent axial parenchyma mark the Pinnatae anatomically as a highly specialized group. The possession of storied rays in two species is another trend of specialization. Based on the data derived from this anatomical study and from the literature, the 16 species of Florida Keys Pinnatae are members of a homogene- ous, phyletically advanced group. Furthermore, that this group constitutes a genetically related complex of plants is borne out by correlative studies in floral and vegetative morphology, as well as by the sub- stantial anatomical studies of which this investiga- tion is a part. These members belong in the Sapin- dales as described by Cronquist. Literature Cited Ayensu, E. S. 1967. Aerosol OT Solution-An Effective Softener of Herbarium Specimens for Anatomical Study. Stain Technology 42: 155-156. 1953. The Anatomical Approach to the Study of Genera. Chronica Botanica 14: 121-125. 1957. The Potentialities and Limitations of Wood Anat- omy in the Study of the Phylogeny and Classifica- tion of Angiosperms. Journal of the Arnold Arbo- retum 38: 243-254. Bailey, I. W. NUMBER 5 25 Bailey, I . W., and W. W. Tupper 1918. Size Variation in Tracheary Cells: I. A Com- parison Between the Secondary Xylems of Vascular Cryptogams, Gymnosperms and Angiosperms. Pro- ceedings of the American Academy of Arts and Sciences 54 : 149-204. A Monographic Study of Rhus and Its Immediate Allies in North and Central America, Including the West Indies. Annuals of the Missouri Botanical Garden 2 1 : 265-498. Barkley, F. A. 1937. Bentham, G., and J. D. Hooker 1862-1 883. Brizicky, G. K. Genera Plantarum. 3 vols. London, England: L. Reeve and Co. 1962a. The Genera of Rutaceae in the Southeastern United States. Journal of the Arnold Arboretum 1962b. The Genera of Simaroubaceae and Burseraceae in the Southeastern United States. Journal of the Arnold Arboretum 43 : 173-186. 1962c. The Genera of Anacardiaceae in the Southeastern United States. Journal of the Arnold Arboretum 43:359-375. 1963. The Genera of Sapindales in the Southeastern United States. Journal of the Arnold Arboretum 44:462-501. 43: 1-22. Candolle, A. P. de, and A. de Candolle 1824-1873. Prodromus systemates naturalis regni vege- tabilis. 17 vols. and 4 index vols. Paris, France: Treuttel and Wurtz. The Taxonomic Value of Wood Anatomy. Pro- ceedings o f the Linnean Society of London 155: 2 14-218. Measuring the Length of Vessel Members. T r o p - ical Woods 40: 19-26. Factors Affecting Dimensional Variations of Ves- sel Members. Tropical Woods 41 : 17-37. Committee on Nomenclature, International Association of Wood Anatomists 1957. International Glossary of Terms IJned in Wood Chalk, L. 1944. Chalk, L., and M. M. Chattaway 1934. 1935. Anatomy. Tropical Woods 107: 1-36. Cronquist, A. 1968. T h e Evolution and Classification of Flowering Plants. Boston, Massachusetts: Houghton Mifflin co . The Wood Structure of Some Australian Rutaceae with Methods for Their Identification. T h e Coun- cil for Scientific and Industrial Research, Aus- tralia, 114: 1-32. The Wood Anatomy of Some Australian Meliaceae with Methods for Their Identification. T h e Coun- cil for Scientific and Industrial Research, Aus- tralia, 124: 1-20. The Anatomy of Timbers of the Southwest Pacific Dadswell, H. E., and A. M. Eckersley 1938. Dadswell, H. E., and D. J. Ellis 1939. Dadswell, H. E., and H. D. Ingle 1948. Area: I . Anacardiaceae. Australian Journal of Scientific Research, Series B. , Biological Sciences l(4) :391-415. Engler, A,, and L. Diels 1936. Frost, F. 1930a. 1930b. 1931. Syllabus der Pflanrenfamilien. 1 1 th ed. Berlin, Germany: Geb. Borntraeger. H. Specialization in Secondary Xylem of Dicotyle- dons: I. Origin of vessels. Botanical Gazet te 89: Specialization in Secondary Xylem of Dicotyle- dons: 11. The Evolution of the End Wall of the Vessel Segment. Botanical Gazet te 90: 198-212. Specialization in Secondary Xylem of Dicotyle- dons: 111. Specialization of the Lateral Wall of the Vessel Segment. Botanical Gazet te 91 : 88-96. 67-94. Gilbert, S. G. 1940. Evolutionary Significance of Ring Porosity in Woody Angiosperms. Botanical Gazet te 102 : 105- 120. Gutzwiller, M. A. 1961. Die phylogenetische Stellung von Suriana mari- t ima L. Botanische Jahrbucher fur Systematik, Pflanrengeschichte und Pflanzengeographie 81 : 1- 49. Provisional Scheme of the Natural (Phylogenetic) System of Flowering Plants. N e w Phytologist 4: 151-162. 1912. L?origine et le systeme phyletique des Angio- spermes. Archives Neerlandaises des Sciences Ex- actes et Naturelles, Series IIIB, 1 : 146-234. Note on Starch Grains in Septate Fibers. Tropical Woods 85 : 1-9. Wood Anatomy and Pollen Morphology of Rhus and Allied Genera. Journal of the Arnold Arbo- retum 21 :279-297. 1942. Comparative Anatomy of the Secondary Xylem of the ?Gruinales? and ?Terebinthales? of Wett- stein with Reference to Taxonomic Grouping. Lilloa 8:82-198. Hallier, H. 1905. Harrar, E. S. 1946. Heimsch, C., Jr. 1940. Hess, R. W. 1946. Identification of New World Timbers: Part 11. Anacardiaceae. Tropical W o o d s 87 : 11-34. The Phylogeny of Flowering Plants. Proceedings of the International Congress of Plant Science, I thaca 1:413-421. 1959. T h e families of flowering plants. 2nd ed. vol. 1. pp. 353-363. Oxford : Clarendon Press. Hutchinson, J. 1926. Jadin, F. 1901. Contribution a l?etude des Simarubacees. Annale.r des Sciences naturalles; botanique. Paris, Serie 8 . 13:201-304. Johansen, D. A. 1940. Plant microtechnique. New York: McGraw-Hill Book Co. SMITHSONIAN CONTRIBUTIONS TO BOTANY Keck, D. D. 1937. Trends in Systematic Botany. Suraey of Biological Progress, 3 : 47-97. New York: Academic Press. 1930. Comparative Anatomy of the Woods of the Mel- iaceae. American Journal of Botany 17: 724-738. 1935. Salient Lines of Structural Specialization in the Wood Rays of Dicotyledons. Botanical Gazette 96 : 547-55 7. 1937. Salient Lines of Structural Specialization in the Wood Parenchyma of Dicotyledons. Bulletin of the Torrey Botanical Club 64: 177-187. Kribs, D. A. Linnaeus, C. 1753. Species plantarum. 2 vols. Stockholm, Sweden: Laurentii Salvii. Melchior, H. 1964. Engler?s Syllabus der PfEanzenfamilien. 12th ed. Pages 246-284. Berlin, Germany: Geb. Borntraeger. 1930. A n a t o m y of the dicotyledons. 2 vols. Oxford, Metcalfe, C. R., and L. Chalk. England : Clarendon Press. Record, S. J. 1939. American Woods of the Family Anacardiaceae. Tropical Woods 60: 11-45. 1941. American Timbers of the Mahogany Family. T r o p - ical Woods 66 : 7-33. Record, S. J., and M. M. Chattaway 1939. List of Anatomical Features Used in Classifying Dicotyledonous Woods. Tropical Woods 57 : 11-16. Timbers of the N e w World . New Haven, Connec- ticut : Yale University Press. Record, S. J., and R. W. Hess 1943. Sass, J. E. 1958. Botanical microtechnique. 3rd ed. Ames, Iowa: Iowa State University Press. Small, J. K. 19 1 1. Simaroubaceae. North American Flora 25 : 227- 1913. Flora of the Florida Keys. New York: Published 1933. Manual of the Southeastern Flora. New York: 239. by the Author. Published by the Author. The Comparative Anatomy of the Xylem and the Phylogeny of the Julianiaceae. American Journal of Botany 39: 220-229. Stern, W. L., and K. L. Chambers The Citstion of Wood Specimens and Herbarium Vouchers in Anatomical Research. T a x o n 9 : 7-13. 1966. Systema et phylogenia magnoliophytorum. ?Nauka,? Moscow and Leningrad ( In Russian). 1968. Synopsis of a Putatively Phylogenetic Classifica- Stern, W. L. 1952. 1960. Takhtajan, A. Thorne, R. F. tion of the Flowering Plants. Aliso 6:57-66. A List of Diagnostic Characteristics for the De- scription of Dicotyledonous Woods. Transactions of the Illinois State Academy of Science 34: 105- 106. The Role of Wood Anatomy in Phylogeny. Ameri - can Midland Naturalist 36: 362-372. 1936. Systematic Anatomy of the Woods of the Simaru- baceae. American Journal of Botany 23 : 577-587. 1941. Systematic Anatomy of the Woods of the Bur- seraceae. Lilloa 6 : 441-465. Tippo, 0. 1941. 1946. Webber, I. E. Wettstein, R. 1935. Handbuch der systematischen Botanik. 4th ed. Leipzig and Wien: Deuticke. Wilson, P. 191 1. Surianaceae. North American Flora 25 :225. NUMBER 5 FIGURE 1-4-1, Toxicodendron radicans: habit showing flowers; 2 , Bursera simaruba: habit indicating size of tree; 3, Bursera simaruba: leaves and fruit; 4, Swietenia nahagoni: habit in- dicating size of tree. 27 28 SMITHSONIAN CONTRIBUTIONS TO BOTANY FIGURES 5-8.-5, Zanthoxylum flavum: leaf showing glandular dots; 6, Sapindus saponaria: habit with fruits and leaves (note winged rachis of pinnately compound leaves) ; 7, Sapindus saponaria: fruits; 8, Cardiospermum halicacabum: habit with fruits and flowers. NUMBER 5 FIGURES 9-1 1.-9, Cupania glabra: fruits and leaves; 10, Simarouba glauca: flowers; 11, Suriana maritima: flowers (note simple leaves). 29 30 SMITHSONIAN CONTRIBUTIONS TO BOTANY FIGURES 12-15.-12, Bursera simaruba: transverse section showing radial multiples and solitary pores (note starch in the fibers), X 246; 13, Bursera simaruba: transverse section viewed under crossed nicols (polarized light) showing the birefringent property of the cell walls and starch grains, X 269; 14, Zanthoxylum fagara: transverse section showing banded parenchyma and radially oriented pore multiples and chains, X 269; 15, Zanthoxylum fiavum; transverse section showing large amounts of thick-walled fibers. Banded parenchyma and radially oriented pore multiples and chains are also shown (note the presence of starch grains in both ray and axial parenchyma), X 269. NUMBER 5 31 FIGURES 16-19.-16, Cupania glabra: transverse section showing growth rings, and solitary, radial multiples, and clusters of pores, X 109; 17, Simarouba glauca: transverse section show- ing aliform and confluent parenchyma arrangement, X 97 ; 18, Sapindus saponaria: transverse section showing confluent bands of parenchyma, X 97 ; 19, Toxicodendron radicans: transverse. section showing qdestionable diffuse-porous distribution of pores, X 246. 32 SMITHSONIAN CONTRIBUTIONS TO BOTANY FIGURES 20-23.-20, Cupania glabra: radial section showing randomly arranged procumbent, square and upright cells. Note the gumlike substance in ray cells, X 390; 21, Metop ium toxiferum: Tangential section showing rays having uniseriate ?wings,? X 246; 22, Swieteniu mahagoni: Radial section showing rays having square and upright, or both, marginal cells, X 97; 23, Simarouba glauca: tangential section showing the storied arrangement of rays and axial strand parenchyma, X 97. NUMBER 5 33 FIGURES 24-27.-24, Bursera simaruba: tangential section showing intercellular canals in the rays (note the starch grains in the septate fibers), X 269; 25, Citrus aurantiijolia: radial sec- tion showing enlarged crystalliferous idioblasts, X 539 ; 26, Zanthoxylum fagara: Transverse section showing traumatic intercellular canal, X 269 ; 27, Zanthoxylum fagara: radial sec- tion showing the traumatic intercellular canal in longitudinal section, X 539. 34 SMITHSONIAN CONTRIBUTIONS TO BOTANY FIGURES 28-32.-28, Exothea paniculata: radial section showing slitlike simple to slightly bordered fiber pits in face view (arrow), X 1872; 29, Exothea paniculata: tangential section showing the fiber pits in transverse section (arrow). Note starch grains, X 1872; 30, Citrus aurantiifolia: tangential section showing alternate intervascular pitting. Note the coalescence of adjacent pit apertures (arrow), X 734; 31, Metopium toxiferum: tangential section show- ing unilaterally compound intervascular pittings (arrow), X 1872 ; 32, Bursera simaruba: maceration showing the occurrence of fenestriform vessel pitting. These pits occur in the cell walls of both vessel elements and parenchyma. Note the simple perforation plate, X 269. NUMBER 5 35 FIGURES 33-35.-33, Amyris elmifera: radial section showing tyloses and granular, translucent material in the vessel elements, X 292; 34, Metopium toxijerum: transverse section showing tyloses in vessels and the occurrence of gelatinous fibers, X 269; 35, Cardiospermum hali- cacabum: transverse section showing large solitary pores and radial multiples of small angular pores (arrow), X 269. * U.S. OOVERNMCNT PRlNTlNQ OFFICE: 1972-417--398/12