558 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 
exactly that of Eupolypodium. Other instances of similar confu- 
sion might be mentioned. 
The inadequacy of scaly covering as a generic distinction for 
“ Lepicystis ” is shown by the complete gradation that exists, in the 
species with pinnatifid to pinnatisect fronds, from those with the 
lamina very densely covered beneath with copious imbricate scales 
to others in which the scales are very few and so minute as to be 
readily overlooked, all of these agreeing essentially in venation. This 
is particularly true of the Eulepicystis (free-veined) series. It seems 
to the writer quite justifiable to include Lepicystis in Polypodium and 
to assign its species among the commonly recognized subgenera ac- 
cording to venation, using the scale characters as a convenient means 
of grouping them within their respective subgenera and of distin- 
guishing them from each other. 
Of the free-veined lepidote species P. furfuraceum, P. murorum, 
and P. plebejum are familiar examples. These and their allies, to 
the number of 21 species, are treated at some length in the following 
pages, an effort being made to reduce the confusion which has long 
existed. There are, besides, brief notes upon 10 doubtful or recently 
described species which it is impossible to place at the present time. 
KEY TO THE SPECIES. 
Rhizome scales large, delicate, flaccid, thin, mostly pale 
and concolorous, thickened and dark-colored (if at 
all) only near their point of attachment, the cells 
elsewhere very thin-walled. 
Lamina subpinnatisect. 
Segments entire; veins diverging from the mid- 
vein at an angle of 45 to 60°... 2.2.2.2... 1. P. furfuraceum. 
Segments undulate, crenate, or serrate; veins 
diverging at an angle of 30 to 40°. 
Veins usually simple, rarely forked near 
their apex; segments surcurrent, 
rounded-excavate to the midvein at 
the proximal side; stipe much shorter 
than the lamina..................... 2. P. eryptocarpon. 
Veins invariably once forked in their basal 
third, the proximal branch rarely 
forked; segments surcurrent, not ex- 
cised below; stipe as long as the lam- 
ina, or longer.................- eee eee 3. P. platylepis. 
Lamina bipinnatifid to quadripinnatisect. 
Plants relatively coarse; lamina very deeply bi- 
pinnatifid, the segments and narrowly 
alate secondary rachises about 1 mm. 
broad. 2.2.2.2... eee eee eee 4. P. lindenianum. 
Plants delicate; lamina tripinnatifid to quadri- 
pinnatisect, the rachises faintly alate; seg- 
ments almost capillary, greatly exceeded 
by the sori. . 2.2.2.2 eee eee eee 5. P. friedrichsthalianum. 
