186 The Botanical Gazette. [April, 
extreme importance in this respect. The underleaves, 
on the contrary, are of less value than in most hepatic 
genera. They are present, occasionally at least, in all our 
species, but they are, in most cases, minute — 
deeply split into slender hair-like divisions and at first sig 
bear much resemblance to clusters of rhizoids. A closer in- 
spection, however, will show that their laciniz are multicel- 
lular and that they proceed from a basilar membrane one of 
more cells in height. The cells of which these ui 
are composed are not like ordinary leaf-cells; they are smaller 
and have much more delicate walls; but, in two of our species, 
peculiar, more distinctive underleaves with leaf-like pee 
are sometimes produced, and these will be especially noted. 
In the following key, none except vegetative characters are 
considered. 
Key to the species. 
Stems creeping and tadiculose; leaves not decurrent. 1.2 — 
Stems ascending from a rooting caudex, normally non-radiculost; 
leaves more or less decurrent. : t-like 
Leaves rarely reflexed at the postical base, not forming crest 
lines parallel to the stem. wool 
Margins of leaves either entire or denticulate, the teeth exce 
me tend moines 5. lk ts sie _ m- 
Margins of leaves dentate, the teeth not exceeding ten in au 
ber. 
Length of leaves averaging less than twice their width. 
Teeth arising from a broad base; ee 
Teeth arising from a narrow base; leaf-cells ep Virginie 
Length of leaves averaging more than twice their width. a 
Leaves obliquely spreading, forming an angle of 40°-45 
the stem, Scarcely narrowed at the base. 5. P. : = with 
Leaves widely Spreading, forming an angle of 55 5 i 
the stem, distinctly narrowed at the base. 6. P. Sui pat 
Leaves retlexed at the postical base, forming two crest-like lines 
allel to the stem. 
Postical margin of leaves piane and dentate beyond the Te™ 
base 
Be ee RR AGREES es py, Rg vet Bre ee oe * . qexed 
Postical margin of leaves re and-undulate beyond the eadill 
Gase..-4) Fe utes : ; ne ajeds Se 
