604 Evans: REPORT ON THE HEPATICAE OF ALASKA 
phasizes do not actually exist. It would appear, in fact, that 
what he considered to be fertile material of S. cordifolia is really 
S. dentata and that S. cordifolia, as originally understood, was a 
composite species. This being the case two courses are possible. 
S. cordifolia might be regarded as a simple synonym of S. dentata, 
since the fertile plants of S. cordifolia, as understood by Miiller, 
belong to S. dentata; or the name S. cordifolia might be retained 
for the sterile plants which Miiller studied. It is evident that he 
laid most stress on these sterile plants and that he drew all of his 
figures from them except figure 7. The writer suggests, there- 
fore, that the second course be followed and that the species 
S. cordifolia be retained with emended characters. 
The plants of S. cordifolia are robust and more or less pigmented 
with purplish red. The leaves are imbricated and are especially 
remarkable on account of their very short and usually arched keels. 
The antical lobe spreads obliquely while the postical keel extends 
at almost a right angle from the stem. Both lobes are strongly 
dilated just beyond the keel, thus giving the leaf a cordate ap- 
pearance. Both lobes are minutely and sharply denticulate, and 
most of the teeth are unicellular, although an occasional tooth 
may be two cells long. In some cases both lobes are abruptly 
and narrowly decurrent, but this condition is by no means con- 
stant, some of the leaves being only slightly or not at all decurrent. 
The leaf-cells are subject to considerable variation in size. In 
one case the cells at the apex of the postical lobe were found to 
measure about 16 win diameter, those in the middle about 30 X 24 #; 
and those at the base about 40X24 4. In other cases the median 
and basal cells were only 18 » wide, and the measurements given 
by Miiller show further slight differences. Along the margin of 
the lobes the cell walls appear to be uniformly thickened with 
poorly developed trigones, but toward the middle the deeply 
pigmented and clearly defined trigones usually form a conspicuous 
feature of the cells. Even here, however, the trigones are not 
always distinct and the walls may appear to be of about the same 
thickness throughout. The cuticle is distinctly verruculose. 
The perianths are borne on the main stems or on leading 
branches, and the bracts are much like the leaves. The innermost 
bracts differ in having a slightly longer keel and more obliquely 
