MAXON—STUDIES OF TROPICAL AMERICAN FERNS. 409 
pubescent (especially beneath), the hairs bifurcate from a basal cell, one branch 
unicellular, the other 2-celled, the second (terminal) cell strongly clavate and 
gland-like. 
Type in the U. S. National Herbarium, no. 407781, consisting of a single plant 
collected near the Finca Sepacuité, Alta Verapaz, Guatemala, March 20, 1902, by 
Messrs. 0. F. Cook and R. F. Griggs (no. 80). A second (smaller) plant of the same 
collection is in the Underwood Fern Herbarium, New York Botanical Garden. 
Polypodium cookii also is of the P. trichomanoides group, but is wholly unlike any of 
the American species thus far described. In its simple veins it is like P. hartti Jenman 
and P. limula Christ, but these species are otherwise very different in nearly all 
characters, especially in their very narrow fronds, in their oblique, elongate sori 
(which occupy nearly the whole vein), in the absence of very long hairs upon the 
lamina, and in the wholly different cellular structure of their rhizome scales. Poly- 
podium cookii is probably more nearly related to those species of the trichomanoides 
group which have the fertile veins forked, but it differs from all of these in having the 
scales perfectly entire, as well as in its simple veins. The sorus is exactly sessile upon 
the upper side of the vein. 
Polypodium perpusillum Maxon, sp. nov. PuateE 13, A. 
Plants very small, apparently clustered. Rhizome decumbent, 5 to 8 mm. long, 
very slender, with a copious covering of relatively large spreading scales nearly 
throughout, these light brown in mass, 1.5 to 2.2 mm. long, narrowly oblong-lanceolate 
or deltoid-lanceolate from a rounded distinctly cordate base, acute, entire (without 
teeth or cilia), 12 to 17 cells broad in the somewhat concave basal portion, the cells 
oblong to linear-oblong, uniformly pale yellowish brown, translucent, the partition 
walls a little darker visually, thin; fronds several, subfasciculate (1 to 3 mm. apart), 
2.5 to 4.3 cm. long, erect or toward the base arcuate, both stipe and lamina devoid of 
long bristle-like hairs; stipe 3 to 6 mm. long, 0.2 to 0.3 mm. thick, narrowly greenish 
marginate from a dark brown base; lamina linear, 2 to 4 cm. long, 2 to 3 mm. broad, 
throughout very obliquely pinnatifid almost to the rachis, glabrous above, a few 
appressed short turgid 3 or 4-celled gland-like hairs borne along the rachis beneath 
and upon the stipe; segments 7 to 16 pairs, alternate, the lower ones mostly sterile, 
narrowly deltoid-oblong, distant, long-decurrent, the fertile (monosorous) segments 
of the middle and upper lamina similar but closer, contiguous to slightly imbricate, 
arcuately oblong from a broadly adnate base, rounded-obtuse, often emarginate upon 
the distal margin above the sorus, then subspatulate; veins of the sterile segments 
mostly simple, terminating in a small but distinct dark hydathode (this equidistant 
from the three sides of the apex of the segment), or rarely forked at an acute angle just 
below the middle; veins of the fertile segments mostly simple, the sorus borne near 
the middle of the vein, the receptacle usually evident as a protuberance upon the 
upper side; sori round or suborbicular, less than 1 mm. in diameter, spreading against 
the rachis, distinct, or confluent only at maturity; annulus consisting of 14 or 15 cells; 
spores subglobose, very minutely roughened. Leaf tissue rigidly coriaceous, not at 
all translucent. 
Type in the U. S. National Herbarium, no. 534909, collected in the Serra de Caraga, 
Minas Geraés, Brazil, March, 1892, by Ule; transmitted by Dr. H. Christ as Polypodium 
setosum Mett., which is P. micropteris C. Chr. 
Polypodium perpusillum has little in common with P. micropteris and may be 
distinguished immediately not only by the shape of the lamina and of the segment 
but by the complete absence of bristle-like hairs. It is more nearly allied to the 
West Indian P. grisebachii Underw.; but that species differs widely in its rhizome 
scales, its flexuous rachis, its delicate, translucent leaf tissue, and its less oblique and 
broader, differently shaped segments, and especially in the position of its sori, these 
borne at or near the end of sharply defined slender branches. 
EXPLANATION OF PLATE 13, A.—See p. 410. 
