et Pee a ee a mi 
Evans: HEpATICAE OF Pugerto Rico 561 
margin. The water sac opens out into the revolute portion of the 
lobe, and it is often difficult to distinguish where the sinus ends 
and the postical margin cf the lobe begins. The plane portion 
varies greatly in form and in size but is normally appressed to the 
lobe. Frequently, however, no plane portion is developed, the 
free margin being revolute and the whole lobule entering into the 
formation of the water-sac. The free margin is so variable, even 
in a single species, that it is difficult to assign it definite characters. 
Itis sometimes entire or nearly so, passing by an indistinct rounded 
angle, which represents the apex, into the vaguely defined sinus. 
In other cases the apex is much more distinct, being tipped by a 
single cell or even by a cell-row consisting of several cells. When 
the apical tooth is well developed there is sometimes a second 
tooth at some little distance from it on the proximal side. The 
hyaline papilla is also proximal in position but is sometimes mar- 
ginal and sometimes slightly displaced from the margin and hidden 
Within the water-sac. Many of these variations are clearly shown 
by M. auriculata. 
The leaf-cells are usually longer than broad and are plane or 
nearly so. They are characterized by distinct trigones, but the 
intermediate thickenings are infrequent except toward the base of 
the lobe. Sometimes the trigones are confluent but rarely suffi- 
ciently so to obliterate the pits. The cell-wall is the seat of the 
Pigmentation, and the middle lamella by its still deeper color 
is sometimes but not always distinguishable. No ocelli are 
developed. 
The underleaves vary from distant to closely imbricated. 
They are attached by an almost straight line and broaden out from 
acuneate base. In outline they vary from orbicular to obovate, 
the apex being broad and frequently retuse. On robust Bteqis 
they are convex in the middle (from below) and their margins, 
Which are entire or nearly so, are more or less revolute along the 
Sides or at the apex. 
The primary female inflorescence is borne on a secondary stem 
°r one of its leading branches and innovates on one side oF ore 
farely on both. The innovations are sometimes long and similar 
to the stem, but they are more frequently abbreviated and repeat- 
edly floriferous, The complicate bracts are deeply and unequally 
