170  LEJEUNEAE OF THE UNITED STATES AND CANADA 
C. calcarea (Lib.) Schiffa. In the latter species the lobes of the 
leaves are narrower than in C. Biddlecomiae and much more 
pointed, varying from acute to acuminate ; they spread more widely 
from the stem and the postical margin is incurved beyond the keel; 
the lobule is more inflated with its free margin strongly involute, 
the roughness of the leaves is more pronounced, and the stylus is 
commonly shorter. € 
Although Spruce at one time tentatively accepted C. Biddle- 
comiae as a species, he afterwards regarded it as a luxuriant form ma 
of C. calcarea. This opinion was based on the fact that it is some- 
times difficult to distinguish certain specimens of the American 
species from certain specimens of the European. The forms which 
resemble each other so closely, however, seem to be always im- 
When robust and well developed specimens are examined, there is — 
little difficulty in distinguishing between them. C. calcarea grows” : 
preferably on limestone rocks, it seems to be much rarer we 
siliceous rocks and there are few records of its occurence on trees. = 
C. Biddlecomiae, on the contrary, attains its best development om m 
trees, particularly in cedar-swamps, and although it is not infre- 
quent on siliceous rocks, it is often less robust in such localities. 
Whether it is abundant on calcareous rocks does not appear from 
the specimens examined. The poorly developed specimens, grow- 
ing on rocks, are the ones which can scarcely be distinguished 
from rudimentary plants of C. ca/carea, as for example the spec — 
mens distributed by Gottsche and Rabenborst in Hep. Eur. 323: — 
Since however no typical specimens of C. calcarea have as Yt —| 
been collected in America, it seems wisest to refer these doubtful 
rock-forms to C. Biddlecomiae. a 
papilla can often be detected somewhere near its apex. Rega 
us, opinions have varied. New 
ce looked upon it as one of = 
