534 Evans: HeEpaTICAE OF PUERTO RICO 
invalidate its claims for recognition and, with emended characters, 
it should reappear in the literature of hepaticology. The first 
species which Trevisan quotes under Symdiezidium is S. trans- 
versale, based on the /ungermannia transversalis of Swartz. This 
species therefore should be regarded as the type of the genus. //. 
transversalis, however, has a number of close allies and forms with 
them the recognized genus Platylejeunea,* one of the most natural 
genera of the Lejeuneae. In consequence of these facts the writer 
suggests that the name Platylejeunea be replaced by the older 
generic name of Trevisan. 
As thus restricted the genus Symdiezidium comprises twelve 
species, nine of which grow in the American tropics and the other 
three on various islands of the Pacific. No species are known at 
present from either Asia or Africa. The genus includes some of 
the most robust of the Lejewneae, the stems in certain species being 
sometimes 10-15 cm. in length. The plants tend to be glossy 
and are nearly always more or less pigmented with brown or olive. 
The stems are at first prostrate and sometimes the prostrate habit 
is retained throughout life by both stems and branches. In other 
cases the plants become pendulous, but a marked contrast between 
a creeping caudex and secondary, pendulous stems never becomes 
apparent. The branching is irregular and is often abundant on 
old plants. In nearly every case, however, the ends of the stem 
and of the principal branches remain simple for a considerable dis- 
tance, thus giving the members of the genus a peculiar and char- 
acteristic appearance, 
The leaves are more or less imbricated, and their lobes spread 
widely from the stem (PLATE 31, FIGURES I, I 1), not shrinking ap- 
preciably nor changing their position upon drying. They vary in 
outline from ovate-oblong to broadly ligulate and tend to be convex 
along the antical side and at the apex and concave along the pos- 
tical side. They are rounded to subcordate at the base and arch 
across or a little beyond the axis (ricuRE 2). The apex is broad 
and almost always rounded but in certain species is occasionally 
apiculate or even subacute. Except for these rare apical teeth 
the margins are entire or nearly so. 
The lobule, even in the same species, varies greatly in size and 
* See Schiffner ; Engler & Prantl. Nat. Pflanzenfam. 13: 130, 1895. 
