a ell 
Ee RL See ee TTT SE tS A” ee i ee ks ee 
Evans: HeEpaTicaE OF Purrto RIco pak 
species. In most of the species the female branch is simple; in a 
few it is subtended by a short sterile or male innovation ; and a very 
few species have been described in which both conditions are found. 
One of the most characteristic features of the genus is the 
perianth, which, however, finds its counterpart in Odontolejeunea, 
in Cycloleyeunca and in certain species of Cololejeunea. This organ 
broadens out gradually from a narrow base and varies at the apex 
from ‘truncate to emarginate. The apical beak is short or obso- 
lete. The perianth in most of the species is strongly compressed 
with sharp lateral keels and a broad and rounded postical keel. 
The lateral keels are usually provided in the upper part with two 
narrow and interrupted, denticulate to laciniate wings. The char- 
acters derived from the floral organs are the most reliable in dis- 
tinguishing the species of this difficult genus, and it is rarely advis- 
able to attempt the determination of material which is wholly sterile. 
Taking the genus asa whole it shows a close relationship with 
Cyclolejeunca and Zrachylejeunea. From the first of these it differs 
in its general habit, in its invariably short female branch, and in its 
lack of gemmae. In fact, so far as is known at present, no species 
of Prionolejeunea exhibits specialized organs of vegetative repro- 
duction, although in one or two cases flat protonemata have been 
observed growing out from ordinary leaf-cells. The absence of 
ocelli will also separate the present genus from most of the species 
of Cycloleyeunea. When compared with 7rachyleyeunca the resem- 
blance in leaves and underleaves is at once apparent, even the 
lobules being built up on the same type in the two genera ; but 
Lrachylejeunea is amply distinct in its inflated, five-keeled perianth. 
nly one species of Prionolejeunea, P. denticulata (Web.) 
Schiffn.,* has been recorded from Puerto Rico. This was found 
in the collection of Schwanecke, and the old determination of 
Hampe and Gottsche + has recently -been confirmed by Schiffner.t 
Unfortunately the original Jungermannia denticulata of Weber § is 
Shrouded in so much mystery that it is impossible to state defi- 
nitely just which modern species or group of species it represents. 
The original description does not help at ail; it merely gives a 
* Engler & Prantl, Nat. Pflanzenfam. 13: 127. 1893. 
{ Bot. Jahrb. 23: 585. 1897. 
@ Hist. Musc. Hepat, Prodr, 30. 1815. 
