224 Evans: HEpaTICAE OF PuERTO Rico 
sides: inflorescence dioicous: ¢ inflorescence borne on a very 
short branch without innovation; bracts obliquely spreading, the 
lobe obovate, 0.6 mm. long, 0.45 mm. wide, rounded or apiculate, 
margin irregularly denticulate, lobule oblong to lanceolate, 0.35 
mm. long, 0.1 mm. wide, blunt or pointed, margin entire or 
slightly crenulate; bracteole free, ovate to oblong, 0.5 mm. long, 
0.3 mm. wide, bifid about one half with narrowly triangular, erect 
and acute lobes separated by a narrow sinus, margin irregularly 
crenulate as in the leaves, especially in the upper part, rarely uni- 
dentate on the sides ; perianth oblong in outline from a somewhat 
narrowed base, 0.9 mm. long, 0.4 mm. wide, somewhat flattened 
but with rounded lateral keels, apex truncate or rounded, abruptly 
contracted into a very short beak, surface roughened from convex or 
rarely conical cells especially along the lateral keels: <j inflores- 
cence and mature sporophyte unknown (PLATE 12, FIGURES 14-28). 
On shaded rocks. El Yunque, Avazs (179). 
The generic position of this distinct little species is not alto- 
gether certain. Its leaves and underleaves are clearly those of a 
Prionolejeunea, and in sterile condition there is little to distinguish 
it from such species as P. Helleri, L. decora and L. macrocardia. 
In its abbreviated female branch it also shows a clear relationship 
with this same genus. Its aberrant character is shown in its perianth, 
which, although somewhat flattened, entirely lacks the conspicuous 
auricles found in all other known species. It hardly seems advis- 
able, however, to make it the type of a distinct genus on this ac- 
count alone, and there is certainly no other established genus with 
which it shows so many points in common as with Prionolejeunea. 
Aside from its peculiar perianth, P. exauriculata differs from 
the other species found in Puerto Rico in its dioicous inflorescence — 
and in the less prominent crenulations of its leaves and bracts. 
The lobules, leaf-cells and underleaves offer few additional points 
of difference. From P. Helleri and from L. decora it may 
further distinguished by its blunter or even rounded leaves, and 
from L. macrocardia by its dioicous inflorescence and by its lack 
of a subfloral innovation. 
In the preparation of this paper the writer has received assist: 
ance from Mr. M. B. Slater, Professor W. G. Farlow, Dr. G. Lin- 
dau and Herr F. Stephani. In fact, the discussion of the difficult 
genus Prionolejeunea would hardly have been possible had it not — 
been for their kind codperation, 
YALE UNIVERSITY, 
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