FOSSIL PLANTS OF THE GROUP CYCADOFILICESBy DAVID WHITEIntroductionThe group of fossil plants appropriately designated the " Cycado-filices " embraces a number of Paleozoic generic types combiningstructural characters of the ferns and of the gymnosperms. Asoriginally established by Potonie 1 it was confined chiefly to generafounded on petrified trunks, petioles, and roots, with the provisionalreference of several frond types. Subsequent research has estab-lished the correlation of the fronds of several of the members, andrecently two distinct types of seeds have been definitely identifiedwith two of the Cycadofilic genera, while a third type of fruit hasbeen found united with a genus of fronds not before suspected ofbelonging to the Cycadofilices. The fact of the discovery of theseeds has been brought to the attention of biologists in this countryby several American paleobotanical writers2 whose brief communi-cations on the subject are confined largely to the nomenclatorialclassification of the group, rather than to the characters of the latter.So far-reaching are the paleobotanical findings concerning the mem-bers of this group, and so important are they to all evolutionists,that it seems desirable to put American botanists in closer touchwith the principal and very interesting features relating to thesesingular types which appear to stand intermediate to the ferns andthe gvmnosperms. To do this in brief form is the purpose of thispaper.The number of genera to be included in the Cycadofilices. orPteridospermese, as designated by Oliver and Scott, is necessarilyindefinite, since future discovery will doubtless bring to light char-acters causing the inclusion therein of other genera whose structureor fructification is at present unknown and whose systematic classi-fication is therefore now provisional only. On the other hand, amore complete knowledge of the reproduction in some of the typesnow included may require their promotion to a higher, gymno-spermic, rank. It must be remembered that some of the genera are1 Lchrbuch der Pflanzenpaleontologie, 1899, p. 160. - Lester F. Ward in Science, July 1, 1904, P- 25; Aug. 26, p. 279. E. W.Berry in Science, July 8, 1904, P- 56; July 15, P- 86; J. M. Coulter in Science,July 29, 1904, p. 140. 378 SMITHSONIAN MISCELLANEOUS COLLECTIONS LVOL. 47known only by the anatomical structure of their stems and petioles;that fronds have been definitely correlated with but four generictypes; and that fruits are known in but three. Concerning themicrosporangiate organs, we have hardly more information than wehave respecting the Cycadofilic fruits.The group appears to have been confined to the upper Paleozoic,and almost exclusively to the Carboniferous, including, in a broadsense, the Permian. The widely diversified associated or contem-poraneous ferns are overwhelmingly eusporangiate, most of themshowing closer affinities with the Marattiacese than with any otherliving family, though imperfect rings of various forms several cellsin width, or may be in thickness, characterize some of the rarer ferngenera. The pteridophytic comparisons are therefore with theMarattiacese, the Ophioglossacese and, to a less extent, with theOsmundacese and the Lygodiacese. The gymnospermic charactersare principally Cycadean, though Cordaitean, and, in a minor de-gree, Araucarian characters appear less prominently in a few of thegenera. Types Generally Regarded as CycadofilicClado.xylon.—One of the oldest though less known types withwhich we have to do is Cladoxylon of Unger, from the LowerCarboniferous of Thuringia. 1 The reference of this genus to theCycadofilices rests on the characters of the stems which are poly-stelic. The steles, or vascular axes, as seen in transverse sectionare dilated radially, each stele including a broad central band ofprimary wood with one or several groups of spiral tracheae, or primi-tive xylem elements, at the border. In the earlier stages the stem,even when of considerable size, is typically filicoid ; but in most ofthe older stems each stele develops a zone of secondary wood withmore or less numerous medullary rays. The tracheides of bothprimary and secondary wood are scalariform. The petioles show astructure distinctly characteristic of ferns, and, but for the secondarywood, the pteridophytic nature of the stems would be unquestioned.The Medullosece.—Among the Paleozoic stems longest and bestknown by their internal structure are those of Cotta's genus Medul-losa. These stems, 2 sometimes a foot or more in diameter, arepolystelic (see plate i.iv), the steles being irregular in form and dis- 'See Solms-Laubach, Abh. d. k. Pr. geol, Landcsanst., Heft, 23, 1896, p. 51.2 See Weber and Sterzel, Beitragc sur Kcnntniss der Medullosece; Ber.naturw. Gesell. zu Chemnitz, vol. xiu, 1896, p. 44. See also Solms-Laubach,Bot. Zcit., 1897, p. 175; Scott, Phil. Trans., vol. 191, B, 1899, p. 81; Goeppertand Stenzel, Palaontographica, vol. xxviii, 1881, p. 12.3. white] fossil plants of group cycadofilices 379 tantly anastomosing. When numerous the smaller arc mostly cen-tral, and the larger, more or less ribbon-like and dilated, are con-centrically disposed near the periphery. Each stele contains a cen-tral axis of parenchymatous conjunctive tissue traversed throughoutby anastomosing groups of primary strands. The larger groups,which are peripheral, include pitted tracheides, and are exarch. 1Each stele is provided with a well-developed zone of secondary wood,loose and spongy in texture, with wide and high medullary rays(see plate li\ , fig. 2). The tracheides are multiserately punctate withbordered pits on their radial walls. The secondary wood is followedby cambium, phloem with phloem rays, and pericycle, while the entiregroup of steles is enveloped in a periderm surrounded by corticalshort-celled parenchyma containing secretory canals suggestive ofthe gum canals of Cycads. In one species the outer steles are greatlybroadened on the peripheral side so as practically to coalesce in acontinuous zone or cylinder of normal secondary wood, the second-ary wood of the inner side of the steles being inverted with reference-to the whole trunk and often forming an inner cylinder of inward-growing exogenous wood. In another form (plate liv, figs. 3 and4) the entire stelic zone is surrounded by several successively devel-oped extra-fascicular zones or layers of wood and phloem, an anom-alous development which has an analogy in the living Cycas andEncephalartos also.The leaf traces of Medullosa consist at first of both primary andsecondary wood, each derived from its own kind on the peripheralside of the stele, in concentric arrangement ; but in passing outwardthe secondary wood in most cases is lost, and the primary woodseparates, while the pitted tracheids disappear, into many small col-lateral strands, the protoxylem being outward, next the phloem.Several leaf traces originating at different levels furnish large num-bers of strands to a single petiole.The petioles of Medullosa, before their final correlation with theparent stems, had been described as Myeloxylon and Myelopteris. 2They comprise a ground mass of short-celled tissue including secre- 1 In describing the arrangement of the woody elements in a bundle col-lateral in structure the terms "exarch," "mesafch" and " endarch " are usedby Williamson and Scott according to the position of the primitive spiraltrachea? (protoxylem) at the outer border of the bundle, in the interior ofthe bundle, or at the inner border of the bundle.2 See Renault, Mem. Sav. etr. Acad. Set., vol. xxn, no. 10, 1876; Renault,Cours dc botaniquc fossile, vol m, 1883, p. 165; Zeiller, Fl. Foss. bassinhouill. et perm. d. Autun et d'Epinac, pt. 1, Paris, 1890, p. 282; Zeiller, Ele-ments dc Palcobotaniquc, Paris, 1900, p. 131. 38O SMITHSONIAN MISCELLANEOUS COLLECTIONS [VOL. 47tory canals and somewhat concentrically arranged vascular bundles,the whole being surrounded by a thick hypodermal parenchymatouszone containing numerous longitudinal sclerenchymatous strands andsecretory canals, and a layer of pallisade tissue. In their generalstructure they resemble Marattiaceous petioles.Naturally the Medullosan stems were early regarded by mostpaleobotanists as more or less distinctly Cycadean ; and this viewis supported by the structure of the petioles, in which, in somespecies, a secondary wood accompanies the vascular strands. Itmust, however, be remembered that collateral primary bundles ac-companied by secondary wood also occur in the Ophioglossacese.The researches of Renault 1 have shown that the petioles (Myel-oxylon) of Medullosa bear the large filicoid fronds, often tripinnateand quadripinnate, of the two great frond genera Neuroptcris andAlethofteris, which previously had been generally considered ascomprising the most common and characteristic Carboniferous ferns. 2A portion of a frond of Neuroptcris, from the Upper Carboniferousof Alabama, is shown in plate lv.As long ago as 1889 Mr. Robert Kidston3 described an imper-fectly preserved specimen showing what appeared to be stalked syn-angia or quadrivalvate capsules in union with Neuropteris hctcro-phylla. The pteridophytic nature of this fructification has beengenerally unquestioned, although, on the evidence of the relationof the fronds to Medullosa, the genus Neuroptcris has been put withthe Cycadofilices by many authors. The recent discovery by thesame distinguished paleobotanist4 of large solitary Rhabdocarpousseeds attached to the fronds of the same species of Neuropteris morethan confirms the exclusion of these anomalous types from the ferns. 1 Comptes Rendus, vol. 94, 1882, p. 1737.2 It is of interest to note, in this connection, that in the Lacoe fossil plantcollection of the U. S. National Museum one of the rock slabs, about nocm. long and 55 cm. in width, contains a fragment from the interior of afrond of Alethoptcris aquilina in which a rachis 3 cm. or more in width,lying near the border of the slab, gives off 6 alternate primary pinnae, noneof which is small enough to be included in its entirety within the area of therock, while in the longest fragments of pinna;, 65 cm. to the broken end,there is no diminution in width. It is impossible to say how high the wholesegment may have been above the lowest primary pinnae; but since none ofthe pinnules of the secondary pinnae is even lobed it is evident that the speci-men comes from the upper part of the frond. Doctor Scott (Phil. Trans.vol. 191B, 1899, pi. ix) figures a flattened petiolar base of Medullosa that isnearly 9 cm. in width. "Trans. Roy. Soc. Edinb., vol. xxxiii, pt. 1, p. 150.* Proc. Roy. Soc, vol. lxxii, Dec. 29, 1903, p. 487; Trans., vol. 197E, 1904,p. 1. WHITE] fossil plants of group cycadofilices 3 s lThe seeds described by Kidston differ but little in superficial char-acters, by which alone they are known, from Rhdbdocarpos tuni-catus. The genus Rhdbdocarpos, which embraces a large numberof Carboniferous species, includes generally large oval or oblong,ribbed and sometimes more or less distinctly trigoniate fruits char-acterized by an outer fleshy and an inner sclerotic test, and by chalaza,micropyle, nucellar membrane and pollenic chamber, while in certainsilicified specimens, even pollen grains and archegonia have been ob-served. It represents one of the simple types of gymnospermousfruit. In these early Paleozoic types the fruit appears to have at-tained its full size before fertilization, and the pollen grains appearto have rested for some time in the chamber before the release ofthe antherozoids. No embryo has been observed.Besides the fronds of Neuropteris, Alethopteris, and Odontopteris,which have been correlated with Myelopteris, and the genera Callip-teris and Linopteris (Dictyopteris Gutb.) referred to the Medullosseby European paleobotanists,1 it is probable, in the judgment of thewriter, that the related genera Callipteridium, and Lesleya togetherwith Megalopteris and its closer relatives are also to be placed withinthe same enlarged group.Colpoxylon.—The stem fragments described as Colpoxylon byBrongniart. 2 are interesting chiefly from the fact that they are mono-stelic in one part and polystelic in another, the solitary stele of thelower part of the stem being divided into several steles in passingupward. The structure of the latter, as well as of the petioles, isessentially like that of Medullosa to which the genus is evidentlyclosely related.The Lyginodendrece.—Passing from the Medullosea, whose foliageis tvpified in Neuropteris, we will next consider the Lyginodendrece, 3whose fronds, so far as known, are included in the great frond genusSplienopteris.Heterangium of Williamson, 4 the most filicoid genus of the family, J The genus Nceggerathia, originally placed among the Cycadofilices byPotonie on account of the arrangement of the " sporangia " on the ventralsurface of the scales in the large strobili, is regarded by most paleobotanistsas gymnospermous, though the nature of the reproduction is not definitelydetermined. 'See Renault, Fl. foss. bassin houill. et perm. d. Aitlitn et d'Epinac, pt. 2.Paris, 1896, p. 299.s An excellent and succinct description of this family is given by Dr. D. H.Scott, Studies in Fossil Botany, London, 1900, p. 307.4 Williamson. Phil. Trans., vol. 178B, 1887, p. 289; Williamson and Scott,Phil. Trans., vol. i86b, 1896, p. 703; Renault, Fl. foss. bassin houill. et perm.d'Autun et d'Epinac, pt. 2, 1896, p. 248. 382 SMITHSONIAN MISCELLANEOUS COLLECTIONS [VOL. 47 resembles a fern in the habit of its delicate quadripinnate frond, theanatomy of its leaf, and its primary wood, while by the structure ofthe leaf trace bundles and secondary wood, with pitted tracheides,it appears to be related to the Cycadales.The average Heterangium stem is less than 1.5 cm. in diameter,and includes : ( 1 ) a large central primary cylinder of anastomosingprimary wood strands mingled with conjunctive parenchyma verymuch as in Medullosa, the outer wood strands, of mesarch col-lateral structure, with spiral, reticulate and pitted (multi-seriate,bordered) tracheides, forming a row, from which the leaf tracesoriginate; (2) a thin zone of secondary wood, with tracheidesbordered-pitted on the radial walls, and with broad medullary rayswhich give it a loose spongy texture; (3) a cambium; (4) phloem;(5) pericycle; (6) an inner cortex of short-celled parenchyma con-taining vertical rows of transverse sclerotic plates, comparable to thestone cells of living plants; (7) an outer cortex containing verticalstrands forming radial and distantly anastomosing hypodermal plates.Adventitious roots spring from the primary wood strands. Thepetiolar strands, which, in one species, contain traces of secondarywood, are at first collateral, but become concentric on entering thepetiole, which contains a single strand. The delicate frond is abso-lutely filicoid, tripinnate, and finely cuneately dissected, that ofHeterangium Grievii being indistinguishable from, if not identicalwith, Sphenopteris elegans. 1The fructification of Heterangium is not definitely known, but itis possible that the male sporangia belong to the type described byStur2 as Calymmatotheca. The structures of primary stem, thickpericycle, and of petiole also are fern-like and have been comparedby Doctor Scott with Gleichenia; but the mesarch outer primarystrands, and the characters of the secondary wood, with pittedtracheides, strongly suggest the stems and petioles of Cycads.Lyginopteris.—Very closely related to Heterangium is the genusLyginopteris of Potonie 3 (Lyginodendron Williamson), for whosebeautiful and complete elaboration we are indebted to Williamson 4and Scott. 5 In the form of its fronds, its microsporangia, and in 1 Phil. Trans., vol. 163, 1873, P- 377; vol. 164, pt. 2, 1S74, P- 675; vol. 166,1876, p. 1; vol. 178B, 1887, p. 289; vol. i8ib, 1890, p. 89.2 Phil. Trans., vol. i86b, 1896, p. 703.8 Lehrb. d. Pfianzenpalmont., p. 171.* See Slur, Abh. d. k.-k. gcol. Rcichsanst., vol. vnr, pt. 2, Wien, 1877, p.130.5 Loc. cit, p. 149. See also Kidston. Trans. Roy. Soc. Edinb., vol. xxxit,pt. 1, 1889, p. 137. WHITE] FOSSIL PLANTS 01 GROUP CYCADOFILICES 3 8 3 the young roots Lyginopteris is typically a fern. In its stems,petioles, and seeds it is largely Cycadaceous, though the stems pre-sent some analogies with Osmunda also.The stems of Lyginopteris (see plate liii), which arc several cen-timeters in diameter, 1 arc monostelic, the center being occupied bya large pith, at the periphery of which occur several (5-8) large,more or less isolated, collateral bundles of small spiral, scalariform,and bordered-pitted tracheides in mesarch structure. Next we havea thick zone of secondary wood consisting of radially and pluri-seriately pitted tracheides and broad medullary rays, both direct andsecondary. The cambial zone is followed by phloem, which also israyed. External to this is the pericycle, several cells thick, a thinperiderm, a tender, inner, and a resistant outer cortex, which ischaracterized by radial sclercnchymatous plates longitudinally flexu-ose-anastomosing so as to form a rhomboidal net in tangential sec-tion, the meshes being occupied by parenchyma (" Dictyoxylonstructure ").The leaf traces, arising from the chief primary strands, breakthrough the secondary wood, and are collateral and twinned whileascending in the pericycle, but they become concentric and V- orW-shaped, without secondary xylem, in the petiole.The adventitious roots, which were published as Kaloxylon byWilliamson prior to correlation with the stems, are described byDoctor Scott as exhibiting in their early stages, less than 5 mm. indiameter, 2-8 strands of primary wood in an arrangement closelyresembling that of the roots of the Marattiaceae, or of the Ophioglos-saceae, though when larger they show secondary tissue in a structure "absolutely indistinguishable from that of typical dicotyledons orgymnosperms."The petioles (originally described as Rachiopteris aspera Will.)of Lyginopteris oldhamia are found in organic union with the verylarge, highly compound, finely dissected fronds of SphcnoptcnsHocningliausii Brongn.,2 one of the common species in the LowerCoal Measures of Europe and America. These fronds are so typ-ically filicoid that only anatomical identity in every detail or actualunion could suffice to remove them from their previously unques-tioned place among the ferns. The reference of the Calymmato-theca form of long, sack-like, clustered bodies, regarded as exannu-late sporangia, to the Hocninghausii group of Sphenopterids has l L. robnstum Seward is represented as about 12 cm. in diameter.2 Plate liii, Figure 2. See also Zeiller, Flore fossils du bassin houill. deValenciennes, 1888, p. 82, pi. V, f. 3. pi- vi, f. I, 2. 3^4 SMITHSONIAN MISCELLANEOUS COLLECTIONS [VOL. 47 recently been supported by Miss Benson, 1 who discussed the con-nection of these organs with Lyginopteris not long" before theindisputable correlation, by Oliver and Scott, 2 of seeds (Lagenos-toma of Williamson) with the same plant, on the basis of the stronglycharacteristic anatomical features. The fruit described as L. Lomaxiis orthotropous, small, only about one-half a centimeter in length,and is borne in pedicellate cupules. The seed, with chalaza, testa,nucellar epidermis, pollenic chamber, etc., is essentially gymno-spermic in structure, though exhibiting certain very unique andstriking features.While related to the ferns by its leaves, young roots, and micro-sporangia, the predominant analogies of Lyginopteris are gymno-spermous. The mesarch arrangement of the elements in the primarywood strands is to be compared with the structure in the petioles andpeduncles of certain living Cycads to which it is almost peculiar.The change in the leaf strand from the collateral to the concentricform while passing to the petiole also finds an analogy in Osmunda.The very large pith and the loose spongy secondary wood suggestthe Cycads, and the seeds are comparable to those of Ginkgo.Megaloxylon.—The genus Megaloxylon of Seward'5 includesstems of considerable size which contain a large primary cylinder ofshort tracheides mingled with parenchymatous tracts. The thicksecondary wood is like that of Lyginopteris. The genus is thusclosely related by its primary stele and its centrifugal xylem to bothHeterangiiim and Lyginopteris; but it differs by the exarch struc-ture of the bundle in both the primary xylem and the leaf trace.Calamopitys.—Closely related to Lyginopteris are the slendermonostelic stems, from the Lower Carboniferous of Thuringia, de-scribed by Unger as Calamopitys. This stem 4 has pith, primary andsecondary wood like that of Lyginopteris. The centripetal trache-ides are pitted on all sides ; the centrifugal on the radial walls only.Calamopitys differs from the genus last mentioned by the change inthe leaf strands to a concentric structure on entering the cortex, andby the separation of the strand into several bundles arranged in aring in the petiole. The structure of the petiole, which accordinglyis fern-like, appears to be identical with that of Kalymma grandisUng., which has also been reported from the Middle Devonian Black 1 Ann. /'('/., vol. xvi, 1902, p. 575. - I'roc. Roy. Soc, vol. lxxi, no. 474, May 26, 1903, p. 477; Philos. Trans.,VOl. 197, B, 1904, p. 193.3 Proc. Cambr. Phil. Sac, vol. x, 1899, p. 158.4 See Solms-Laubach, Abh. k. Preuss. geol. Landesanst., Heft. 23, 1896, pp.63 and 43; also Dawson and Penhallow, Can. Rec. Sri., vol. IV, 1891, p. I. white] fossil plants of group cycadofilices 385Shale of Kentucky. The fronds and fructification of Calamopitysarc unknown.The Cycadoxylece.—The stems published by Renault 1 as Cycad-oxylon are still closer to the Cycads, and their secondary wood isdescribed as distinctly Cycadean. But the Cycadoxylon stem pre-sents a strikingly anomalous feature in the occurrence, within thecylinder of outer (normal) secondary wood, of two or more distinct/.mies of inner crescentic secondary wood, each zone of which with itsrays and accompanying broad phloem bands, lies in an invertedposition in the body of the pith. The genetic connection withLyginopteris is shown not only in the general characters of thecentrifugal wood but also by a slight development of a similarmedullary secondary wood in certain specimens of the latter genus.An important link between the Lyginopterid group and the Cycad-ales (in a broad sense) is furnished by the stems described byRenault2 as Ptychoxylon, another of the Cycadoxylese, which isregarded by both its author and Doctor Scott as essentially Cycad-aceous. In this genus (see plate liv, fig. 1) a very large pith issurrounded by a more or less complete narrow zone of secondarywood similar to that of the other stem genera. But within thecylinder of normal centrifugal wood lie several concentric arcs offully developed inverted secondary wood, each with its phloem,medullary rays, and phloem rays. At the leaf gaps the edges of theinterrupted outer or normal cylinder curve inward to coalesce tem-porarily with two of the inner arcs of inverted exogenous wood,which are termed " reparatory " arcs. In the relations of the nor-mal and inverted secondary woods Ptychoxylon appears to presentsome analogies with Colpoxylon and MeduUosa, No primary woodappears yet to have been observed in the petrified stems, though theleaf trace is said to be essentially like that of Lyginopteris.Except for the anomalous medullary wood Ptychoxylon is Cycad-aceous ; and this systematic reference is supported by the discovery,in the same beds, 3 of leaves (Ptcrophylluin and Sphenozamites)which in form and external characters are distinctly Cycadean, ac-companied by a remarkable inflorescence (Cycadospadix milleryensisRen.) provisionally referred to Ptychoxylon by Renault.Protopitys.—In Goeppert's Protopitys originally described fromthe Lower Carboniferous of Silesia and more fully made known by 1 Flore fossile dit bassin houill. ct permien d'Epinac, pt. 2, 1896, p. 307; Wil-liamson, Phil. Trans., vol. 163, 1873, P- 377', Williamson and Scott, Phil.Trans., vol. i86b, 1896. p. 703; Seward, Ann. hot., vol. xi, 1897, p. 65.2 Op. cit., p. 329.3 Loc. cit., p. 329. 386 SMITHSONIAN MISCELLANEOUS COLLECTIONS [VOL. 47Count Solms-Laubach 1 we have another unique type of stem com-bining filical and gymnospermic characters and referred by DoctorScott to the Cycadofilices, though gymnospermous characters pre-dominate. Its secondary wood, of coniferous structure, contains alarge elliptical pith bordered by a continuous zone of primary woodwhich is thicker and somewhat complex at the ends of the ellipse,whence the leaf strands originate. This genus, on which CountSolms founds a family, appears to the writer to resemble so closelycertain of the woods described as Dadoxylon (Cordaitcs) as to de-mand a reexamination of some of the material showing secondarywood only and referred by authors to the latter genus.Fossil plants petrified in such a way as to show their microscopicalstructure are extremely rare in the Carboniferous series of thiscountry, and but few fragments excepting those of Dadoxylon andPsaronius have come to light. Impressions or carbonized remainsare, however, as common in the Coal Measures of America, par-ticularly in the Appalachian trough, as in other parts of the world.Our knowledge of the Cycadofilices, so far as it proceeds fromAmerican material, is based almost entirely on these carbonizedremains.Aneimites {Adiantites of authors).—The genus Aneimites is rep-resented by several species in the basal Coal Measures of bothEurope and America, though no petrified specimens (having struc-ture) of that genus are known, and until recently we have had noclue to its fructification. Conclusive data relating to the latter havebeen furnished by material from the lower Pottsville along Newriver in southern West Virginia. The fronds, which are commonlyknown as Adiantites, are tripinnate, with slender divisions of therachis and very deeply dissected cuneate pinnules and lobes, which,as the early name for the genus implies, strongly resemble those ofAdiantum? The seeds, borne on dichotomous pedicels at theperiphery of the somewhat reduced fertile fronds, are small, about .5 cm. long, rhomboidal, and vascularly striate, thinly lenticular intransverse section, the outer envelope being laterally dilated, espe-cially below the middle of the seed, so as to form a wing to thefruit. The seed, seen in all stages of development, is deciduous atmaturity by abscission at the broadened apex of the pedicel. Thegeneral characters, so far as recorded by the impressions, appear inthe main to be conformable to the primitive types of gymnosperms. 1 Bot. Zeitung, 1893, P- 197-2 See Smithsonian Miscell. Colls., Quarterly Issue, vol. 47, pt. 3, p. 322, pi.XLVIII. white] FOSSIL PLANTS OF GROUP CYCADOFILICES 3 ,S 7Microsporiferous organs of two forms are intimately associated withthe fronds, one of them belonging to the ( alymmatotheca type. Thelatter, however, is not found in union with the frond. The discoveryof seeds in connection with the Aneimites group of supposed fernsnecessitates the systematic transfer of this group to the Ptcrido-spermeze. This reference is based solely on the evidence of thefructification, the anatomical characters of the fronds, whose fernnature had not before been questioned, being still unknown, thoughthe form of the rachis suggests a single petiolar strand like that ofHeterangium. Aneimites is the third Cycadofilic genus in which theseeds are definitely correlated through union with the sterile por-tions of the frond. Types Probably Cycadofilic It has been seen that the reference to the Cycadofilices of thegenera individually discussed above is based on (a) the anatomicalcharacters of the stems and petioles; and (b) on the discovery ofseeds still attached to or definitely identified with the fronds, thiscategory being represented by but three types, Medullosa (Neurop-teris), Lyginopteris, and Anemites (Adiantitcs). Besides thesethere is a third category, more indefinite and unsatisfactory, butworthy of mention as provisionally referable to the same phylum.It is based (c) on their evidently close relationship to one of theabove mentioned Cycadofilic genera ; on the circumstantial evidenceof association; or on the negative evidence of the absence of anyrecognized filicoid type of fructification.The third Pteridospermic category includes common genera, notpetrified so as to show their internal anatomy, found as impressionsor carbonized remains at many hundreds of localities in Europe orAmerica, but whose fructification is not yet known. Some of thesegenera, which are still placed among the ferns, appear to be habitu-ally associated with certain generic types of seeds in a way tostrongly suggest a former union as well as a common source. ThusGrand 'Eury, who more than any other paleobotanist has contributedto our knowledge of the habits of the Paleozoic plants in situ, intwo recent papers1 concludes not only from the absence of rhizomesand connected fructifications, but from the large number of generaof Coal Measures seeds that are unaccounted for and the habitualassociation of some of the latter with fronds of the Neuropterideae,that Pachytesta is referable to Alcthopfcris; that certain small striate l Comptes Rendus, vol. 138, March 7, 1904, p. 607; vol. 139, July 4. "'"i-P- 23. 388 SMITHSONIAN MISCELLANEOUS COLLECTIONS [VOL. 47 winged seeds (Odontopterocarpus) belong to Odontoptcris; thatcertain Trigonocarpous seeds, occasionally showing Rhabdocarpouscharacters also, belong the Neuropteris and Linopteris;1 and thatsome rarely observed minute floral vestiges and smooth capsules,resembling the Arkansas specimens referred by Lesquereux2 toSorocladus, represent the polleniferous organs of Neuropteris.Concerning the typical Neuropterids this distinguished savant be-lieves that they " grew from seeds and arc primitive Cycads withfern fronds." :Mention has already been made, in the discussion of the Medul-loseas, of the probable Cycadofilic nature of Callipteridium, Lesleya,and the Megalopterids, on the basis of what the waiter regards astheir distinct affinities with the Neuropterid group, and on accountof the absence of all traces of fructification in these genera. On thebasis of similar strong though negative evidence it becomes not im-probable that the supposed fern genera Mariopteris, Pscudopecop-teris (including the round-lobed Diplothmemae), Eremopteris andTriphyHaptens (with Sphenopteridium) , no trace of whose fructifi-cation has yet been found, and whose internal organization is un-known, will eventually be found to belong to the Pteridospermese.It is possible, however, that in the cases of some of these genera theidentity of the reproductive organs is masked by dimorphism, which -1 mis to have been as prevalent among the ferns of the Paleozoicas it is among those of to-day.On the other hand, it is far from impossible that some of the typeswhich, solely on the evidence of the anatomical characters of theirstems, have been referred to the Cycadofilices may eventually becorrelated with some of the isosporous fronds already in hand amongthe ferns. The lessons learned from Calamites, Lepidodendron, andSphenophyllum, which, notwithstanding the development of prom-inent as well as varied secondary woods, are none the less Equise-tales, Lycopodiales, and heterosporous Sphenophyllales respectively,teach us that the accession of secondary wood, even of a structurerded by many botanists as gymnospermic, should not be acceptedle facto proof of an ordinal difference in rank. This importantfact should be constantly kept in view, and more particularly whendiscussing the systematic relations of some of the genera founded 1 The sporangia approximating the Crossothcca type, described by Zrilh-r(Fl. foss. bassiit Iwuill. d. Commentry, pt. 1, 1888, p. 273) in one of theafore-mentioned genera, Linopteris, probably represent-, as suggested byGrand 'Eury, only the male sporangia of the genu^.2 Coal Flora, vol. 1. p. 328, pi. xlviii, f. 8.9 Comptcs Rendus, July 4. p. 23. WHITE] FOSSIL PLANTS 01 i ' ' P iDOFILICES 3^9 only "ii petrified stems, such for example as Cladoxylon and Calamo-pitySj which differ essentially Erom ferns only by the presence oftheir secondary wood. It must al>o be remembered that both sec-ondary wood, of a sort, and collateral bundles are found in theOphioglossacese. ConclusionsThe development of secondary xylem in various Cryptogamicfamilies among Carboniferous plants, in various species of the samegenus, and at various stages and positions, in the growth of the plantconclusively supports the view, long ago suggested by Williamsonin the case of Catamites, that secondary wood originated as an engi-neering feature—a mechanical aid for the support of the giganticCarboniferous representatives of some of our humble modern fam-ilies. As such its origin was doubtless polyphyletic and, naturally,since the types appeared in different geological stages, polychronous.The varied phases in which this secondary wood appeared—inpolystelic, inverted intra-medullary, extra-fascicular or accessory,and laterally alternating-, as well as modern phases, with their re-markable differences in combination, and in varying degrees of com-plication-—constitute a group of structural anomalies which in them-selves offer the evolutionist strong testimony of fortuitous variation.It is as though Nature were at the Carboniferous moment in themidst of a series of amazing engineering experiments, most of whichwere either buried deep in Paleozoic oblivion, or permitted to surviveonly as vestigial relics and atavistic ghosts. ,Our knowledge of the structures and fructifications of the Cycado-filices (Pteridospermese) leaves little room for doubt as to the descentof the Cycads, and perhaps some of the other modern gymnosperm-ous types, 1 from the ferns, though, as Doctor Scott has taken painsto point out, it does not follow that any of the Coal Measure typesyet discovered actually represent the lineal ancestors of our livinggymnospermic genera.The discovery of seed-bearing members of the Cycadofilices, whileanswering in part the old question as to the origin of the gymno-sperms, injects, at the same time, a new biological problem into thefield of inquiry,— viz., the origin of the Cycadofilices. Seeds of sohigh and so gymnospermoid an organization as Lagenostoma or1 There is important data in support of the view that >a portion, at least,of the conifers were derived from the Paleozoic Lycopodiales through agroup of Lycopodineous seed plants whose existence is predicated partlyon paleontological indications, partly on theoretical grounds, rather than defi-nitely known or established, and for which Professor Ward (Science, Aug.26, 1904, p. 281) has proposed the class term " Lepidospermse." 39° SMITHSONIAN MISCELLANEOUS COLLECTIONS [VOL. 47Rhabdoatrpos were, on the whole, hardly to be expected in view ofthe typically filicoid habits of the fronds, the presence of distinctlypteridophytic characters in the stems and petioles, and the antiquityof the seed-bearing types.Since Lyginoptcris, Calamopitys, and Protopitys are present inrocks of Lower Carboniferous age, it follows that the heterosporousfilices, which must have antedated the Cycadofilices, are to be lookedfor at the very base of the Carboniferous, if not, as is more probable,in the Upper Devonian. Triphylloptcris, which the writer believesto be Pteridospermic, occurs near the base of the Lower Carbonifer-ous in America. Concerning the Pteridospermic nature of thespecimens reported as Kalymma grandis from the Black Shale ofKentucky, there appears to be room for doubt. Should, however,the interpretation of these fossils prove valid, the Cycadofilices willgo back to the Middle Devonian (Genessee), or nearly as far as theoldest plant fossils generally recognized as unquestionably ferns.The presence of gymnosperms at this early date is generally acceptedon the evidence of the occurrence of fossil woods representing sev-eral species of Dadoxylon, which includes the trunks of Cordaites.Some of these early species have, as has already been suggested,very much in common with Protopitys.In a discussion of the recent discoveries relating to the Cycado-filices, which he seems inclined to regard as gymnosperms, ProfessorZeiller remarks that it may become necessary to refer to the Carbon-iferous as the epoch of the gymnosperms. rather than of the Crypto-gams. Whatever the limits and final interpretations of the Cycado-filices, they constitute a well-marked filicoid group preeminentlycharacteristic of the Carboniferous, which may appropriately bepaleobotanically designated as the epoch of the Pteridosperms—theseed-bearing ferns. Explanation of Plat.: LIIl Fig. i. Cross-section of a stem of Lyginoptcris oldhamia, about ^/2 timesthe natural size. At the margin of the large central pith area,which contains numerous sclerotic nests, are the primary woodstrands (.r), eight in number; external to these is the broadzone of secondary wood (with cambium and secondary phloem),interrupted by the passage of the leaf traces ; ph, a primary phloemgroup ; pd, periderm, limiting the pericycle which contains othersclerotic groups; It i-lt 5, leaf traces (numbered in the order oftheir phyllotaxy) becoming twined while ascending in the peri-cycle; the periderm is followed by the inner cortex and the outercortex, the latter with its radial plates, the longitudinal anasto-moses of which are not seen in the cross-section. From theLower Coal Measures at Oldham. After Williamson and Scott.Fig. 2. Fragment, in natural size, from a portion of the frond of Sphenop-tcris Hoeninghausii, the leaf of Lyginoptcris. From the Pottsvillenear Quinnimont, West Virginia. SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 47, PL. 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