Evans: HepaTicAE OF PUERTO RICO 31 
Although P). d:dens is asomewhat smaller plant than D. hamati- 
Folia, the two species are closely related. In the latter species, 
however, the lobes of the leaves are shorter and less attenuate, and 
the antical margin is usually distinctly dentate, especially in the 
lower part. The leaf-cells are of about the same size in the two 
species but in D. hamatifolia the trigones are more conspicuous. 
The underleaves also offer good points of difference, the basal por- 
tion in D. hamatifolia being often bordered by more than six mar- 
ginal cells and the widely spreading divisions measuring four or 
five cells in length and usually two cells in width at the base. In 
the European species, finally, the leaves are destitute of ocelli and 
the inflorescence is autoicous. 
Among the Puerto Rico species D. Araucariae and D. dissiti- 
folia are both close to D. didens, as is also the species next de- 
scribed. Aside from the difference in size already noted D. Arau- 
cariae differs from D. d¢dens in its more distant leaves with more 
denticulate margins and in its more laciniate bracts and bracteoles. 
In D. dtssitifolia also the leaves are more distant than in D. didens 
and are distinguished further by being exocellate, but in this 
species the larger and more complicated underleaves offer the best 
differential characters. 
Propagula are so abundantly produced in D. éidens that the 
microphyllous branches upon which they are borne deserve a few 
words of description. A branch of this character usually bears 
normal leaves at its base but as we proceed toward the apex we 
find the leaves gradually becoming smaller and arrested in their 
development. The aborted leaves are much shorter and narrower 
than normal leaves, their less attenuate lobes are suberect or ob- 
liquely spreading and are never falcate, their lobules are much 
reduced, in extreme cases consisting simply of a minute tooth 
borne near the postical base of the lobe. Nearly every one of 
these aborted leaves gives rise to a propagulum just behind it and 
as the propagula become. detached very readily we can usually 
observe no signs of them except the basal sheaths which are left 
behind. The underleaves on the microphyllous branches are 
smaller than ordinary underleaves, their divisions being only one 
or two cells long. The propagula themselves are similar to those 
of D. dissitifolia and of other Puerto Rico species. It may be 
