Hepaticae of Puerto Rico 
|, THE SPECIES OF LEPTOLEJEUNEA, INCLUDING AN ACCOUNT OF THEIR VEGETATIVE 
REPRODUCTION 
By ALEXANDER W. EVANS 
(WiTH PLATES 23-25 ) 
The genus Leffolejeunea is composed of minute tropical species 
which occur almost invariably on living leaves. A few of the 
species grow on ferns or on hairy plants, but most of them prefer 
the smooth and glossy evergreen leaves of trees and shrubs. 
They confine themselves to the upper surface of the leaves and at 
first form circumscribed patches, which are clearly defined. As 
the plants grow older the patches become confluent and lose their 
distinct outlines. The sterile axes of Leptolejeunea together with 
their leaves are at first very closely appressed to the matrix, but 
some of the later branches are ascending and those bearing peri- 
anths are suberect. The plants, however, never become densely 
matted together as is usual in the Lejeuneae. 
The genus has several peculiarities in common with Drepave- 
lejeunea. The underleaves for example are essentially the same 
in both and afford a convenient character for distinguishing them 
from other minute Lejeuneae. These underleaves are commonly 
minute even for the size of the plant and are built up in a Very 
regular way. We can distinguish in them two slender divisions 
and a basal portion, the latter consisting of a central rhizoid-beat- 
ing region surrounded (except at the base) by a single row © 
marginal cells. The basal portion is usually in the form of a 
trapezium and is attached to the axis by the shorter of its parallel 
sides. In some species it is more nearly rectangular and is then 
abruptly contracted just above the base. From the upper angles 
of this basal portion arise the two filiform or subulate division®» 
which are sometimes composed of a single row of cells throughout 
and are sometimes two or three cells wide in the lower part. i 
divisions vary from suberect to widely spreading and in cert” 
species form an angle of 180° or more with each other. In the 
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