saffoed: lignum nephriticum 503
and aluminum and iron hydroxides amounting to about 10 per
cent.
The name vegasite^ is suggested for the mineral from Las
Vegas, the principal town of the county in which it Occurs.
Briefly, vegasite may be characterized as a mineral giving chemi-
cal reactions similar to those of plumbojarosite, but distinguish-
able by widely different optical constants.
BOTANY.—Eysenhardtia polystachya, the source of the true
Lignum nephriticum mexicanum.^ William Edwin Saffoed,
Bureau of Plant Industry.
INTRODUCTION AND HISTORY
Among the wonderful products of the New World brought to
Europe shortly after the discovery of America was a Mexican
wood supposed to be efficacious as a diuretic and therefore called
lignum nephriticum. Water kept in cups of this wood and an
infusion of its chips in spring water had the remarkable property
of reflecting a blue color, though apparently colorless or yellow
when held up to the light in a glass receptacle. This led to the
experiments of Athanasius Kircher,^ in 1646, and afterwards
to the more systematic study by the Hon. Robert Boyle, in 1663,
which may be regarded as the first serious investigation of the
phenomenon now known as fluorescence.^ One result of Boyle's
work was to make fignum nephriticum a classic wood. Strange
to say, however, the botanical identity of the plant from which
this wood was derived has remained uncertain until the present
day. Though celebrated throughout Europe in the 16th, 17th,
and the early part of the 18th centuries, sacrcely a fragment of
8 The "e" in the first syllable should be given the Spanish pronunciation:
like "a" in late.
1 Based upon a paper entitled "The rediscovery of Lignum nephriticum,"
read by the author February 2, 1915, at a meeting of the Botanical Society of
Washington. Published with the permission of the Secretary of Agriculture.
2 "Of a certain wonderful wood coloring water all kinds of colors," in Ars
Magna Lucis et Umbrse, pp. 77 and 78. 1646.
^
Boyle, Robert, Experiments and considerations touching colours, p. 203. 1664.
504 safford: lignum nephriticum
it is now to be found in drug collections, and its very name has
disappeared from encyclopedias.
Monardes (1565) was the first to call attention to the wood,
but he knew nothing of its origin except that it came from Mexico.
Hernandez, writing about the year 1576, described the plant
producing it under the name coatl, or coatli, as follows: A shrub
or tree with leaves like those of a chick-pea {Cicer arietinum)
but smaller, and with spikes of small longish flowers. The color
of the flowers he described as yellow and faded but he; evidently
drew his description from dried material, as was the case with the
majority of plants described by him, which were gathered and
brought to him by Indian herb doctors. Hernandez Was a phy-
sician rather than a naturalist, and many of his descriptions and
illustrations of both plants and animals are so crude as to be un-
recognizable. Of lignum nephriticum he gave no illustration.
He was even uncertain regarding the plant producing it, stating
that they had described it to him as a shrub, but that he had seen
specimens of it exceeding very large trees in size. Hernandez's
work on the products of Mexico remained in manuscript for
almost two centuries and never appeared as a whole. The
portions of it relating to medicine were grouped together and
prepared for publication by Nardo Antonio Recchi; but owing
to lack of funds or for some other reason Recchi's compilation
did not appear until 1751, seventy-three years after Hernandez's
death, though a Spanish translation from Recchi's Latin manu-
script by Fray Francisco Ximenez appeared in 1615, in the city
of Mexico.
In the meantime the plant itself remained unidentified botanic-
ally. Caesalpinius (1583) and Caspar Bauhin (1623) supposed
it to be a species of Fraxinus. Terrentius, in Recchi's epitome
of Hernandez (1651), referred it to the Leguminosae but did not
attempt to identify it. Johan Boeclerus (1745), believing it to
be a Laburnum, called it Cytissus mexicanus. Linnaeus, in his
Materia Medica (1749), added to the confusion by referring it to
Moringa pterygosperma, an East Indian tree, in spite of the fact
that it was originally declared to be of Mexican origin ; and Gui-
safford: lignum nephriticum 505
bourt, in his Histoire abregee des drogues (1820), identified it
with the West Indian cat's-claw (Mimosa unguis-cati L.).
The first to indicate its true botanical classification was Dr.
Leonardo Ohva, Professor of Pharmacology in the University of
Guadalajara. In his Lecciones de Farmacologia^ he^ identified
it with Varennea polystachya DC. {Viborquia polystachya Ortega;
Eysenhardtia amorphoides H.B.K.). Subsequent authorities,
however, did not accept his identification. Dr. Fernando
Altamirano (1878), while recognizing the identity of the coaili
of Hernandez with the tree called by the modern Mexicans palo
dulce and referring it to Viborquia polystachya Ortega, was not
aware that the latter was the same as Eysenhardtia amorphoides
H.B.K., and he followed Alfonso Herrero in referring hgnum
nephriticum to Guilandina moringa, a mistake which may be
traced at once to Linnaeus. In describing the uses of coatli
wood by the modern Mexicans, he states that the country people
make drinking-troughs of it for their fowls, to guard against
certain epidemics to which the latter are subject; or, if the vessel
from which they drink is of some other substance, they put a
piece of the wood in the water and allow it to remain there. The
water assumes a blue color, he says; but Mariano Barcena, who
experimented with it, observed that the blue color was the result
of the refraction of light, and the water, instead of yielding a blue
coloring matter like indigo, yielded a yellowish brown dye-stuff.^
Sargent, in his Silva of North America, gave an amended
description of the genus Eysenhardtia, in which he for the first
time established the combination Eysenhardtia polystachya, but
it is evident that he was unaware that this species had anything
to do with lignum nephriticum, or that its wood yielded a fluores-
cent infusion. Concerning it he simply says: ''The wood of
some species is hard and close-grained and affords valuable fuel.
The genus is not known to possess other useful properties.*^
The third edition of the Nueva Farmacopea Mexicana (1898)
^2: 429. 1854.
^
Altamirano, Fernando, "Leguminosas indigenasmedicinales," in La Natural-
eza, 4: 97-98. 1879.
« Sargent, C. S. The Silva of North America, 3: 30. 1S92.
506 safford: lignum nephriticum
repeats Oliva's observations under the heading ''Taray de Mexi-
"
ico, but in a footnote states that leno Jiefritico had been errone-
ously attributed to Varennea polystachya, or Eysenhardtia amor-
phoides H.B.K., and that its classification was not known. ^
In a subsequent edition of this work the name palo dulce is
omitted, except as applied to the European hcorice, Fllickinger
and Hanbury, in their well known Pharmacographia (1879),
are silent about Hgnum nephriticum, although for years before
the publication of this work Hanbury had been seeking to identify
it.^ Dragendorf refers to it as a species of Guajacum.^ Otto
Stapf, however, guided by Ramirez and Alcocer's Sinonimia
vulgar y cientifica de las plantas Mexicanas (1902), referred a
piece of wood labeled "cuatl" in the Paris Exposition to Eysen-
hardtia amorphoides; but the wood was unaccompanied by
botanical material by which it might be identified with certainty.^
He gives a history of. the wood known as lignum nephriticum in
early literature, and also quotes several Mexican authorities
but not Oliva, cited above. He accounts for the fact that the
flowers were described by Hernandez as yellow by the supposition
that there are varieties of Eysenhardtia yielding lignum nephriti-
cum which have yellow flowers, although, as a matter of fact,
no such forms occur in the localities cited by writers on the sub-
ject; and the only species in which the flowers are yellow are
low scrubby plants which never attain the size even of a small
tree or have a stem with a diameter approaching the dimensions
of the pieces of lignum nephriticum hitherto described.
The last author to investigate the origin of lignum nephriticum
is Dr. Hans-Jacob MoUer, of Copenhagen, who after an exhaustive
study of the subject referred it to a Mexican tree belonging to the
' Nueva Farm. Mex. 153. 1896.
* See Oliver and Hanbury, in—Admiralty
Manual of Scientific Inquiry, p. 391.
1871. "Lignum nephriticum. This rare wood, noticed by some of the earliest
explorers of America, is a production of Mexico. To what tree is it to be re-
ferred? Its infusion is remarkable for having the blue tint seen in a solution of
quinine."
" Das Lignum nephriticum deriilteren Mediciu wird wohl von einer Guajacum-
Art stammen." Dragend. Heilpfl. 345. 1898.
i»See Stapf, Otto. Kew Bull. Misc. Information, 1909, pp. 293-305. 1909.
safford: lignum nephriticum 507
genus Pterocarpus. Dr. Moller made a careful examination of
the various woods hitherto supposed to be the true Ugnum
nephriticum mexicanum, among them specimens of the wood of
Eysenhardtia amorphoides, sent to him by C. A. Purpus, the
latter described as "das Kernholz von einen recht dicken Ast,"
but with negative results (''keine Fluoreszenz)." On examin-
ing the heartwood of a Philippine species of Pterocarpus, how-
ever, he found that in water containing lime it yielded an infusion
having the characteristic sky-blue fluorescence of lignum nephriti-
cum mexicanum as described by early investigators. He there-
fore assumes that the mother-plant of lignum nephriticum
mexicanum, "sought in vain for 300 years by so many investi-
gators, is a Mexican species of Pterocarpus," in all probabil-
ity Pterocarpus amphymenium DC. (Arnphymenium pubescens
H.B.K., Pterocarpus pubescens Sprengel) and he refers a second;
kind mentioned by Hernandez, endemic in Quauchinango, to
Pterocarpus orbiculatus DC.^^
There can be no doubt that the heartwood of some species of
Pterocarpus does yield a fluorescent infusion; but the "lignum
nephriticum mexicanum," or "coatl/' of Hernandez, the leaves
of which are described as "resembling those of Cicer arietinum
but "smaller, and which are also compared with the finely divided
leaves of the common wild rue, cannot possibly be identified with
any known Mexican species of Pterocarpus. The leaflets of the
species of Pterocarpus figured by Moller himself exceed 6 cm. in
length by 3.5 cm. in breadth.
IDENTIFICATION OF LIGNUM NEPHRITICUM
In connection with his work on the economic botany of Mexico
the writer has for years been seeking the source of lignum nephriti-
cum. Among other woods examined for the blue fluorescence
characterizing this wood were specimens of branches of Eysen-
hardtia polystachya, collected by the writer in 1907 in the vicinity
of Aguascalientes, the infusion of which gave no evidence of
fluorescence in ordinary sunlight. From this fact and from the
11
Moller, Hans-Jacob. Lignum nephriticum. Berichte der Deutschen
Pharmaz. Gesellsch. 23: 88-154. 1913.
508 safford: lignum nephriticum
fact that all specimens seen by the writer were either shrubs or
trees too small to yield wood for the manufacture of bowls and
cups, the writer was inclined to agree with Moller in discarding
Eysenhardtia as a source of the famous wood. In July, 1914,
however, specimens of a medicinal wood from Mexico were
brought to the writer accompanied by herbarium material from
the same tree sufficient to identify it. It proved to be Eysen-
hardtia polystachya, commonly known by the modern Mexicans
in many localities as palo dulce, or ''sweet wood." Its collector
had not noticed anything peculiar about the color of its infusion,
but dwelt upon its efficacy as a cure for certain diseases to which
fowls are subject in Mexico. The wood was a section of a tree
trunk, whicli deprived of its bark was 7 cm. in diameter, and
which, unhke all specimens of Ej^senhardtia wood hitherto
seen by the writer, consisted chiefly of dark brown, dense, fine-
grained heartwood very much like Guaiacum officinale in appear-
ance, surrounded by a ring of brownish-white sapwood 5 to 8 mm.
thick. A few small chips of the heartwood in ordinary tap-
water tinged the latter a golden yellow, which soon deepened to
orange, and looked like amber when held between the eye and the
window. When the glass vial containing the liquid was held
against a dark background the liquid glowed with a beautiful
peacock blue fluorescence, very much like that seen in quinine.
Placed partly in a sunbeam, half of the hquid appeared yellow and
the other half blue; and when the sunlight was focused upon it
by the lens of a common reading glass, the vial appeared to be
filled with radiant gold penetrated by a shaft of pure cobalt.
There was no longer any doubt as to the identity of the wood.
It could only be the true lignum nephriticum of Robert Boyle's
experiments; and it was undoubtedly the wood of Eysenhardtia
polystachya, a tree with small pinnately compound leavs which
might well suggest those of a chick-pea or of the common wild
rue of Spain, and with spikes of small flowers which had turned
yellowish in drying, corresponding with Hernandez's description
of the coatl of the Aztecs.
Chips of the sapwood tinged tap-water only slightly at first,
but when left over-night the infusion deepened to a greenish
safford: lignum nephriticum 509
yellow and glowed with a decided fluorescence. With distilled
water neither the sapwood nor the heartwood produced fluores-
cence, as seen by ordinary sunlight; but this phenomenon was
distinctly visible when, at the suggestion of Dr. Arno Viehoever,
U. S. Department of Agriculture, these infusions were held in
the ultraviolet rays of a fluorescence lamp, and it was also dis-
played in ordinary daylight when a small amount of sodium car-
bonate or other alkali was added to the infusions of the wood in
distilled water. On boihng chips of the wood in tap-water for
several hours a deep amber-colored extract was obtained not un-
like Madeira wine in color. When placed on the table the surface
of this extract appeared to be outlined by a deep blue marginal
ring, and when held away from the light the fluorescence of the
liquid gave it the appearance of certain mineral oils. A drop of
the extract in a glass of water caused the whole glass to glow with
fluorescence when held in the rays of the sun admitted through a
hole in a screen.
At a conversazione at the house of Dr. Alexander Graham
Bell, on the evening of January 6, 1915, at which the wood and
accompanying herbarium material were shown by the writer,
specimens of the infusion when exhibited by ordinary electric
light failed to show fluorescence; but afterwards, when held in
the rays of an arc hght the liquid glowed with an intense blue
which illuminated the faces of those standing near by.
Experiments were made by Dr. Lyman J. Briggs, Biophysicist
of the Bureau of Plant Industry, with a view to determine the
possible value of lignum nephriticum as an indicator in titri-
metric determinations. The result of Dr. Briggs' observations
have not been published, but he recognized at once the advantage
which this, like other fluorescent substances, must have over
those indicators which show color changes only by transmitted
light, especially in testing dark liquids, in which the color of the
liquid masks the color changes of the indicator. Eysenhardtia
wood has one great advantage over fluorescein itself, from the
fact that its extract is readily soluble in cold water. With most
acids it does not fluoresce, but in the presence of acetic acid its
fluorescence is not destroyed. It cannot, therefore, be used as
510 safford: lignum nephriticum
an indication of alkalinity in all cases. As compared with
phenolphthalein it has a neutral point nearer the acid end of the
scale; that is to say, it will fluoresce in a solution in which phenol-
phthalein develops no color whatever.
FURTHER BOTANICAL HISTORY
As already stated, the first description of the plant yielding
lignum nephriticum is that of Hernandez, written about the year
1575, but first published in the form of a Spanish translation,
in the city of Mexico, by Ximenez, in 1615. It is as follows:
They call coatl a plant which they describe as a shrub but I have seen;
it larger than very large trees; and some call it tlapalezpatli, or "blood-
red medicine." It is a large shrub which has a thick trunk devoid of
knots, like that of a pear tree. The leaves are like those of the gar-
vanzo [Cicer arietinum], but smaller and almost like those of rue [Ruta
chalepensis L.] and somewhat larger, a mean between these two extremes;
the flowers yellow and faded, small and longish, are arranged in spikes.
. . . It grows in moderately warm regions like the valley of
Mexico, and in still warmer situations like Guachinango [state of
Puebla], Chimalhuacan [district of Texcoco], Chalco, and Tepuztlan
[near Cuernavaca, state of Morelos] and almost throughout the entire
extent of the malpais [pedregal or lava-beds] of Coyohuacan; and in
many other places.
Following Monardes, whose description of the wood he quotes,
the author tells of the blue color of the infusion of the wood and
of its virtues as a diuretic; and he adds: ''There is another kind
of plant of this nature, but it does not color the water;" and on
his return trip to Spain he says: ''In this fleet there is a Viscayan
merchant who is taking more than fifty large logs of this wood
to Spain."
From the above description it is evident that Hernandez refers
to two distinct species, the first of which, with leaves resembling
those of Cicer arietinum and Ruta chalepensis and with spikes of
small longish flowers, is undoubtedly Eysenhardtia polystachya,
which never exceeds the size of a small tree. It was undoubtedly
the wood of this species which Robert Boyle used in making his
experiments on fluorescence. The second is in all probability
one of the trees called by the Aztecs tlapalezpatli, or tlapaliz-
patli (from tlapalli, tincture; eztli, blood; and patli, medicine),
safford: lignum nephriticum 511
and by the Spaniards sangre de drago, or dragon's blood. Among
the latter are species of Pterocarpus, which grow to much larger
dimensions than the Eysenhardtia, and one of these was in all
probability the source of the large logs carried to Spain by the
Viscayan merchant mentioned by Hernandez. Hernandez never
described a Pterocarpus botanically, and in all probability he
never saw specimens of their leaves or flowers. As already
indicated, none of them has leaves with small leaflets in any way
comparable to those of Cicer arietinum or of Ruta chalepensis.
THE GENUS EYSENHARDTIA
Following is the original description of the genus Viborquia
of Ortega/- with a reproduction of Ortega's original illustration
(fig. 1). The name itself, on account of its prior use for
another genus by Konrad Moench of Marburg, in 1794, under
the form Viborgia, had to be abandoned in favor of the much
later name Eysenhardtia of Humboldt, Bonpland and Kunth,
proposed in 1823. ^^
Generic Character
Calyx tubular-campanulate, five-toothed at the mouth; teeth equal,
obtuse, very small, the two upper ones more remote, broader, and
a little deeper.
Corolla papilionaceous. Vexillum cuneiform, emarginate, carinate,
with the margins involute. Wings longer than the keel, spathu-
late, falcate, within concave above. Keel two-petaled, spathulate,
falcate, within concave above.
Stamens ten. Filaments shorter than the corolla, united into a cylin-
der cleft above. Anthers subrotund, incumbent, bifid at the base.
Pistil with the ovary oblong compressed. Stijle subulate, ascending,
a little longer than the stamens. Stigma capitate.
Legume oblong, compressed flat, subfalcate, containing the seed at
the apex.
Seed oblong-reniform, affixed to the apex of the legume.
Differential Character
Calyx 5-toothed, the two upper teeth the broader. Corolla composed
of 5 petals: vexillum cuneiform, the remaining petals spathulate.
Legume sessile, foliaceous, 1-seeded, containing the seed at its apex.
12 Hort. Matr. Dec. 5: 66. 1798.
13 Nov. Gen. et Sp. 6: 489. 1823.
Fig. 1. Eysenhardtia polystachya (Ortega) Sargent, A copy of Ortega's
original illustration, with details of flower and fruit.
512
safford: lignum nephriticum 513
description of eysenhardtia polystachya
The plant positively identified as yielding the hgnuni nephriti-
cum of Hernandez may be described briefly as follows:
Eysenhardtia polystachya (Ortega) Sargent, Silv. N. Am. 3: 29.
1892 (excl. Texas references).
Viborquia polystachya Ortega, Hort. Matr. Dec. 5: 66, pi. 9. 1798.
Eysenhardtia amorplioides H.B.K. Nov. Gen. et Sp. 6: 491, pi. 592.
1823.
Varennea polystachya DC. Prodr. 2: 522. 1825; Oliva, Lecc. Farm.
2:429. 1854.
An erect, sweetly aromatic shrub or small tree, glandular-punctate,
with spreading, recurved branches. Leaves even-pinnate or odd-
pinnate, with numerous small opposite or alternate stipellate leaflets,
these oval or oblong-elliptical, entire, usuall}^ decreasing in size toward
the extremity of the rachis, the terminal one of odd-pinate leaves usually
obcordate, the others rounded or slightly retuse at the apex and often
terminating in a short acumen, pubescent when young, often becoming
glabrate, usualty punctate with glandular dots on the lower surface;
rachis grooved above, irregularly glandular-dotted, often retaining the
persistent minute subulate stipels after the leaflets have fallen. Flowers
fragrant, small, white, turning yellow in drying, borne in terminal
densely spicate racemes; pedicels subtended by a lanceolate deciduous
bracteole, short and slender, often reflexed at length, but sometimes
ascending or widely spreading; calyx glandular-punctate, 5-toothed,
persistent; corolla scarcely at all papilionaceous, composed of 5 nearly
equal unguiculate petals, the standard slightl}^ broader than the wings
and keel, emarginate, carinate, with involute margins; stamens 10,
diadelphous, the superior one free, the filaments of the others united in-
to a tube; ovary subsessile, oblong, compressed, terminating in a long
slender stjde, somewhat longer than the stamens, geniculate and glandu-
lar below the apex; stigmas introrse. Legume small, oblong, compressed
flat, subfalcate or almost straight, subtended by the persistent companu-
late calyx and tipped by the persistent base of the style, usually glandu-
lar-punctate, indehiscent, pendent or abruptly reflexed, sometimes
widely spreading or ascending but never erect and appressed, purplish
at the apex when fresh, usually containing a single seed near the apex.
This species was first described by Gomez Ortega, under the name
Viborquia polystachya in 1798, as shown in the synonymy given above,
from specimens grown in the Royal Garden of Madrid from seeds
sent by Sesse from Mexico. Ortega named the genus in honor of
"A^iborq, most distinguished professor of the botanical garden of
Copenhagen, who, when a short time ago he journeyed through Spain
and visited Madrid, left in us deep appreciation of his kindliness and
his conversation." The generic name Viborquia had to be aban-
Fig. 2. Eysenhnrdtia pulystachya (Ortega) Sargent. A Tamaulipas specimen,
showing reilexed legumes and cross-section of the trunk (lignuln nephriticum) .
Natural size.
514
safford: lignum nephriticum 515
cloned for the reason given above, and that of Eysenhardtia H.B.K.
substituted for it.
The general range of the genus Eysenhardtia is from Guatemala
to Texas and Arizona. On account of their great variability it is
difficult to delimit the species. It is quite certain, however, that the
low shrubby Eysenhardtia texana Scheele, with erect appressed falcate
seed-pods, the type of which was collected by Lindheimer in the vi-
cinity of New Braunfels, Texas, is a valid species quite distinct from
E. polystachya of central and southern Mexico, which often attains the
size of a tree; and it is quite probable that the more robust E. adeno-
stylis Baillon, of Guatemala, is also a valid species. On the other
hand E. orthocarpa Watson, of western Texas and southern Arizona,
approaches so closely to forms of E. polystachya collected in the Valley
of Mexico, Jalisco, and Michoacan, that it may prove to be specifically
identical with them. A critical study of the genus Eysenhardtia is
greatly to be desired. The group of low scrubby plants including
Eysenhardtia spinosa Engelm., E. parvifolia Brandeg., and E. penin-
sularis Brandeg., is so distinct from tj^pical Eysenhardtia that it is
quite possible it may have to be removed from this genus.
Eysenhardtia polystachya, as understood by the author, is remark-
ably variable in size and form of leaves, density of pubescence, and
appearance of seed pods. It sometimes occurs as a stunted bush
with very small leaflets, sometimes as a spreading shrub with straight
stems, and sometimes as a slender tree 5 to 7 meters high, the wood
of which is prized by cabinet makers on account of its hardness, dura-
bility, and fine, dense, straight grain. In the vicinity of Mexico City
on the pedregales, or lava beds, sometimes called the malpais, a form
with small pubescent leaves is the most prevalent. In the northern
Mexican states it occurs on elevated dry plateaus in the form of shrubs
about 2 meters high with relatively small leaflets. A distinction has
been made between the forms having reflexed pedicels and those with
ascending or spreading pedicels; but in the barrancas of Jalisco forms
very closely allied are found almost side by side, some with mature
pods reflexed, and others with them ascending but never closely ap-
pressed as in E. texana. In this region also there are subglabrous forms
with seed pods at least twice as large as those of the type.
In addition to the localities mentioned, specimens of Eysenhardtia
polystachya, or of forms so closely allied to it as to be scarcely distin-
guishable, have been collected on the volcanoes of Cohma, near the
Pacific coast of Mexico, and Orizaba, near the Gulf coast; on the high
water-shed between Chilapa and Tixtla, in the State of Guerrero; in
516 safford: lignum nephriticum
the State of Oaxaca at elevations of 1500 to 1800 meters, especiallj^ on
the slopes of barrancas or canyons; and m northeastern Michoacan,
where the trees are large enough to yield valuable cabinet wood. A
specimen in the U. S. National Herbarium collected at the station of
La Junta, Michoacan, by Langlasse (no. 226) is described by the col-
lector as "arbre au tronc elance; bois, recherche pour ebenisterie,
prouduit une teinture bleue." The specimens in the Economic Her-
barium of the U. S. Department of Agriculture, including the wood with
fluorescent properties, described in the present paper, were collected
in north-central Tamaulipas, not far from the village of San Nicolas.
They are shown in figure 2.
DENDROLOGICAL NOTES
Microscopic sections of the wood of Eysenhardtia polystachi/a
were made at the writer's request, by Dr. Albert Mann, Plant
Morphologist of the Bureau of Plant Industry, and by Mr.
CD. Mell, Assistant Dendrologist of the Forest Service. Dr.
Mann found the heartwood to be extremely compact, heavily
Hgnified, and impregnated with a gum, or resinoid substance,
which did not break down in xylol. This gum is contained in
tracheae, which in cross sections appear like pores, either soli-
tary or in groups of two or three. Radial and tangential sections
show the tubes, with pitted walls, to be partly or entirely filled
wdth this gum, and they also show the medullary or pith rays,
which in the cross-sections are inconspicuous. The annular
lines of growth, however, are well marked in the cross sections.
Specimens of Philippine Ugnum nephriticum (Pterocarpus
iyidicus) commercially known as narra, from Baggao, province
of Cagayan, Island of Luzon, were obtained by the writer from
the newly installed wood-collection in the U. S. National Museum.
This wood bears little resemblance to that of Eysenhardtia. In
the specimens obtained the color was a beautiful deep flesh tint
variegated with light red the grain coarse and somewhat twisted; ;
and the annular lines of growth, as seen in the cross-section, ver}^
distinct, with conspicuous large pores between them. Chips
of this wood in tap water yielded a yellow infusion of a lighter
shade than that of Eysenhardtia polystachya but reflecting a very
similar blue fluorescence.
safford: lignum nephriticum 517
SUMMARY
Lignum nephriticum mexicanum, a wood remarkable for the
blue fluorescence of its infusion in spring water, was celebrated
throughout Europe in the 16th century as a diuretic. Its
botanical identity has remained uncertain until the present time.
It proves to be the wood of a leguminous tree, Eysenhardtia
polystachya occupying an exensiVe range in the interior of Mexico.
The botanical description of the tree corresponds well with that
of Hernandez written in the 16th century. Its pinnately com-
pound leaves bear a general resemblance to those of Cicer arieti-
nuin and also suggest the divided leaves of Ruta chalepensis. Its
small flowers, arranged in spicate clusters, though white when
fresh, soon turn j-ellow in dried specimens. Its wood, straight-
grained and dense and free from knots, yields a tincture in spring-
water (containing a slight percentage of lime) which shows a
remarkable blue fluorescence and in an opaque vessel appears
quite blue.
Its botanical identity remained uncertain for so long a time
owing to the following causes: (1) Commercial specimens of the
wood were unaccompanied by botanical material; (2) botanical
material in herbaria was lacking in wood ; (3) the phenomenon
of fluorescence as seen in ordinary dayhght is produced by an
infusion of the dark-colored heartwood, while the light-colored
sapwood of stems and of moderate-sized branches, though
yielding a fluorescent infusion as seen in ultra-violet rays, does
not yield a fluorescence perceptible in daylight ; (4) the plant was
first described from a shrub in all probability too young to possess
heartwood, and the author of the species was unaware of its
identity with lignum nephriticum or even of its power to produce
the phenomenon of fluorescence.
For the first time the botanical identity of the true lignum
nephriticum mexicanum has been established beyond a doubt,
bj^ the study and exhibition of specimens of wood corresponding
accurately with the descriptions of Robert Boyle, yielding the
characteristic fluorescence obtained by him in his experiments,
and accompanied by botanical specimens from the tree producing
the wood, these agreeing in all respects with the original descrip-
tion by Hernandez of the plant yielding lignum nephriticum.