Касста 25 
On exposed or lightly shaded banks, often associated with XA. 
nigrella, К. trichocarpa and К. Californica. San Francisco (Bo- 
lander), on hillsides between Mission Dolores and Clarendon 
Heights, San Francisco (Howe); Fruit Vale (Miss Edith S. Byx- 
bee, Howe). 
Riccia Americana is closely related to R. /amellosa Када, from 
which, however, it differs very markedly in spore-characters. 
The European plant has distinctly wing-margined and plainly 
angular spores and the markings of the inner and outer faces are 
nearly uniform; the ridges of the outer face are more vermicular 
than in А. Americana and less often form perfect areolae, and 
when the areolae are well defined, they are smaller and more 
numerous, 14 ог 15 measuring the diameter of the face. The 
scales іп А. Americana are more prominent than іп А. /amel- 
(оза. For comparison, we have made use of a specimen from 
Florence, Italy (the type locality), апі one from Sicily, both 
kindly communicated by Dr. E. Levier. 
Riccia Austini Steph. (Bull. Herb. Boiss. 6: 336. 1898) is a 
nearer ally in respect to spore-characters, with the exception that 
the spores are smaller (75-105 in maximum diameter), but differs 
in the much thinner and mostly smaller thallus,this being only 14-20 
cells in greatest thickness and the breadth of the transverse sec- 
tions being 3—4 times their height, and in the less conspicuous 
scales. R. Americana seems to occupy a somewhat intermediate 
position between these two species. In case it should ever be 
combined with A. Аи т, this latter name should be employed 
for the aggregate, inasmuch as it was published, we are informed 
by Dr. Eugène Autran, editor of the Bulletin de L’ Herbier Boisster, 
about two weeks in advance of our Riccia lamellosa Americana. 
We have been able to see only four or five antheridia in this 
species though hundreds of sections have been made. In two in- 
stances, archegonia occurred on the plants bearing the antheridia ; 
and in two other cases no archegonia were to be discovered, but 
in the latter cases we were sectioning somewhat fragmentary alco- 
holic material. The great majority of the plants examined showed 
archegonia without traces of antheridia. 
