MR. J. MIERS ON THE HIPPOCRATEACEÆ OF SOUTH AMERICA. 413 
14. TYLODERMA. à; 
This genus is proposed for a climbing plant from the Isthmus of Darien, with a fruit 
bearing an external resemblance to that of Sicyomorpha from the same region, but with 
seeds of a very different structure. It has slender branches, with opposite leaves of an 
oblong form, upon short petioles ; but the flowers, unfortunately, are wanting. The fruit 
is cylindrieal, with a thick, coriaceous, indehiscent pericarp, and contains two seeds of a 
shining light brown colour, narrowly oblong, somewhat trigonoidal, rather smooth on the 
three faces of each, but much corrugated on the rounded angles, one of these angles being 
thickly carinated, and suddenly expanded towards the base into an irregular and somewhat 
auricular form, at the bottom of which is the hilar cicatrix of its attachment to the base 
of the pericarp: this outer coating (testa) is somewhat osseous, smooth within, half a line 
in thickness, hard, ligneo-coriaceous, and exhibits a channel in the middle of the cari- 
nated angle just mentioned, which runs up from the basal hilum to the summit for the 
passage of the stout cord of the raphe; the next integument is quite free from the testa, 
is of an opaque brown colour, chartaceous in texture, somewhat brittle, apparently with- 
out any vessels, though marked at its apex by a small cicatrix, denoting the point of its 
attachment to the chalaza: there is a third almost imperceptible pellicular membrane, 
which adheres somewhat firmly to the integument and embryo: the latter is trigonoidly 
cylindrical, obtuse at each extremity, consisting of a white solid fleshy or waxy mass, 
homogeneous in texture. When a very thin transverse slice is viewed under the micro- 
scope, no mark of agglutination is observable; but after immersion in a weak solution 
of iodine, a very faint line'is discerned across the middle, indicating the probability of its 
being composed of two very agglutinated cotyledons. A longitudinal section of the ovary 
exhibits the same homogeneity of texture; at the chalazal end no indication whatever of 
any division is observable; but at the extremity, pointing towards the hilum, a conical 
slit is seen half a line within and parallel to the periphery, which can be traced to an 
extent of 3 lines, or one sixth of the total length of the embryo; and this may perhaps 
be regarded as the line of the neorhiza of a large basal radicle. "What proportion of the 
total length of the embryo may be considered cotyledonary, and what belongs to the 
radicle, it is difficult to say; but at least a quarter of the whole length may be assumed 
to form the radicle. Such a structure would be analogous to that described in Priono- 
stemma, only with a much larger radicle. Zyloderma therefore appears to belong to the 
Hippocrateacee, although its flowers are unknown, quite agreeing in the habit of the 
plant, which is deseribed as climbing to a very great height; it has opposite, exstipulate, 
impunctate leaves, similar to those of Sicyomorpha in texture and venation, to which 
genus it appears to approach in affinity. The generic name is derived from vóXoc, callum, 
dépua, tegumentum, because of the hard callous texture of the testa of its seeds. 
TYLODERMA, nob. 
Flores ignoti. Drupa majuscula, subcylindrica, cucumiformis, unilocularis, 1-2-sperma; pericarpium 
indehiscens, crassum, dure coriaceum. Semen elongato-subtrigonum, angulis obtusis rude corru- 
gatis, erectum : testa ossea, crassissima, durissima, in angulo unico obtuse carinata, carina ad imum 
subito expansa et auriculata, medio raphigera: raphe intra carinse canalem, simplex et grosse chordi- 
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