Evans: HeEpaticaE oF Purerto Rico 497 
latter case the upper boundary of the underleaf is a straight or 
slightly convex line. The number of cells in the basal portion, 
the number of cells in the divisions and the angle which the di- 
visions form with each other vary within very narrow limits for a 
given species and are of much value in distinguishing between 
closely related plants. The rhizoids to which the underleaves 
give rise are numerous and of the usual type. They consist of 
simple or branched projections from the median cells of the basal 
portion and are not themselves divided into cells. The rhizoids 
secrete a gelatinous substance by means of which they attach the 
hepatic to its substratum. In a few species of Drepanolejeunca an 
underleaf sometimes develops a small, sucker-like disc, from which 
the rhizoids develop secondarily. Similar discs occur on the under- 
leaves of Odontoleyeunea* and also on the first underleaves of the 
leafy propagula in both Leptolejeunca and Drepanolejeunea. 
In the position of the ¢? inflorescence and in the general 
characters of the perianth, Leptolejeunca also agrees with Drep- 
anolejeunea. The 9 inflorescence is borne on an extremely short 
branch, which in some species is simple and in others gives rise to 
a single innovation. With the exception of the perichaetial bracts 
and bracteoles the leaves on the ? branch are abnormally devel- 
oped or rudimentary, and are commonly reduced to a single side- 
leaf and an underleaf. The perianth is dilated and sharply five- 
keeled in the upper part, and the keels, with rare exceptions, 
extend outward, and often slightly upward, as distinct projections 
or horns, 
The most reliable differences between the two genera are to be 
found in the shape of the leaves and in the characters drawn from 
the keels and horns of the perianths. In Leftolejyeunea the leaves 
are gradually dilated from a narrow base and are rhombic, ovate, 
or lanceolate in outline ; their apices, although sometimes acute, 
are scarcely acuminate and are usually plane. In Drepanolejeunea 
the leaves are abruptly dilated from a still narrower base, and are 
More or less triangular in outline, their apices are long and slender . 
and usually reflexed. In Leptolejeunea the keels and horns of the 
Perianth are smooth or nearly so, while in Drepanolejeunea, they 
S s & Spruce, Hep. Amaz. et And. 142. 1884. Also Goebel, Pflanzenbiologische 
childerungen, 1: 461. Sf. 66. 1889. 
