590 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 
elongate lumen invariably present), the whitish borders as broad or broader, 
composed of several rows of irregular, transparent, thin-walled, mostly trans- 
verse cells, the outermost row with their distal ends projecting, connivent in 
pairs, the free tips deeply bifid, the margin of the scale thus irregularly lacerate- 
denticulate. Fronds several, 5 to 10 mm. apart, rigidly erect, 15 to 23 em. 
long, the stipe longer than the lamina; stipe 10 to 13 em. long, 1.2 to 1.5 mm. 
thick, dull grayish brown, subterete, faintly bimarginate, deciduously palea- 
ceous; lamina 8 to 10.5 em. long, sometimes linear and nearly simple, 0.5 to 1.5 
cm. broad, with a few low or irregularly elongate lobes, but normally deltoid 
to ovate, 3 to 4.5 em. broad, abruptly acuminate and conspicuously long-cau- 
date, very deeply pinnatifid or pinnately parted, densely pajJeaceous beneath, 
minutely and scantily so above, the principal segments (4 to 6 pairs) mostly 
less than their own width apart, 1 to 2.5 em. long, 5 to 8 mm. broad, oblong to 
linear-oblong, rounded at the apex, decurrent, joined by a costal wing, this 
about 1 mm. broad upon each side of the stout, partially concealed, brownish 
rachis at the base, gradually very much broader toward the apex, the upper- 
most segments giving way abruptly to the broad crenations of the elongate 
apex; venation wholly concealed, goniophlebioid or subphlebodioid, a row of 
large oblique elliptical areoles extending nearly to the margin, the few excurrent 
ultimate veinlets free or variously joined: sori 5 to 8 pairs, very large, dark 
brown, broadly oval, nearly medial, partially concealed by the seales, terminal 
upon one or both of the branches of the once forked included veinlet, or the 
fertile veinlet simple. Leaf tissue opaque, rigidly herbaceo-coriaceous; scales 
of the lower surface very numerous, widely imbricate, suborbicular to deltoid- 
ovate, 1 to 2 mm. long, yellowish brown in mass, with small dark brown centers, 
irregularly denticulate, the narrow teeth bipapillate at their extremity: scales 
of the upper surface similar but paler, narrower, and with much longer teeth. 
Though confused with P. thyssanolepis, which is certainly a close ally, P. 
leucosporum differs widely in gross characters from adult specimens of that 
species in its pinnately parted, conspicuously long-caudate lamina and in its 
oblique, long-decurrent segments. As to minute characters, both the rhizome 
and lamina scales have the marginal teeth about half the length (or less) 
of those of P. thyssanolepis; and, under the microscope, the dark median area 
of the rhizome scales is seen to extend nearly to their slender tip, instead of 
being confined to the basal portion of the scale. The broadly joined segments 
of the lamina are sufficiently distinctive. 
Aside from the specimens discussed above, P. leucosporum is known from at 
least two other collections: Colombia, Burschel, mentioned by Hooker: and 
Venezuela, Fendler 251, listed by Eaton! Neither of these has been seen by the 
writer. 
9. Polypodium tridens Kunze, Farrnkr. 1: 23. 1840, 
TYPE LOCALITY: Galipagos Islands, Ecuador (Cuming 112), 
DISTRIBUTION : Galipagos Islands. 
ILLUSTRATION: Kunze, op. cit. pl. 13. f. 1. 
This species which was known to its deseriber only from a single frond, is 
the subject of a subsequent note by Hooker; who, basing his conclusions upon 
more ample material, was inclined to look upon the fronds with forked or tri- 
partite pinne as atypical, the simply pinnate fronds representing the normal. 
The tendency toward bipartite or tripartite pinnse seems, however, to be nor- 
*Mem. Amer, Acad. n. ser. 8: 200. 1860. 
? Hook. Sp. Fil. 4: 211. 1862. 
