550 Evans: HEpATICAE OF PUERTO RICO 
except the African Mastigo-Lejeunea crispula Steph.,* which its 
author reports from Costa Rica.t The plants belonging to this 
genus usually form depressed mats of considerable extent. They 
are often deeply pigmented and sometimes appear almost black, 
with little or no lustre, when they become dry. The pigmenta- 
tion, however, rarely shows the brownish hues which are charac- 
teristic of such genera as Lopholejeunca and Symbiezidium, and the 
plants are occasionally glaucous. 
The distinction between creeping caudex and secondary stems 
is much better marked in Mastigolejeunea than in the two preced- 
ing genera. The caudex clings closely to the substratum by means 
of numerous rhizoids and in an old tuft is difficult to demonstrate 
except along the edges. The secondary stems, although fre- 
quently prostrate, develop very few rhizoids and can be easily 
separated from the substratum. These stems branch irregularly 
and sometimes copiously and branches of a second or higher order 
often occur. The branches are of three types< normal branches 
similar to the stem, microphyllous branches with shorter and rela- 
tively broader leaves, flagelliform branches with very rudimentary 
leaves. These distinctions, however, are not always well-marked, 
and it frequently happens that a branch is microphyllous at the 
base and normal or flagelliform at the extremity. The flagelliform 
branches usually develop an abundance of rhizoids and doubtless 
play an important part in affixing the plants to the substratum. 
The leaves are densely crowded ; when dry they spread ob- 
liquely and are strongly convex, overlapping each other closely ; 
when moist they become squarrose and spread more widely, the 
imbrication being thereby much less apparent. The lobes are 
falcate from a round or subcordate base and vary in outline from 
ligulate to ovate. The postical margin is more or less revolute, 
thus increasing the appearance of convexity, but the antical mar 
gin is plane or nearly so. The apex varies from rounded to suba- 
cute and is never reflexed. The margin is entire or vaguely and 
irregularly sinuate but is never distinctly dentate. 
The lobule usually consists of two portions, a narrow inflated 
water-sac along the keel, and a plane portion along the free 
*Hedwigia 27: 111. 1883. ~~ SOT : : 
t Bull. Soc. Roy. Bot. Belgique 31: 180, 
1892. 
