EvANS: REPORT ON THE HEPATICAE OF ALASKA 609 
caudex, and the absence of rhizoids adds to the plausibility of this 
idea. Unfortunately no signs of such a caudex can be demon- 
strated in the present material. Neither can the position which 
the shoots occupy in nature be made out, although they are 
probably pendulous or ascending. 
Among Alaskan species R. Bolanderi is apparently the closest 
ally of R. polyclada. It is, however, a somewhat smaller plant, 
the stems being only 1-2 cm. in length and 0.12 mm. in diameter, 
while the maximum size of the stem-leaves is about 0.85 X0.65 
mm. It differs further in its less regular habit; in its more ob- 
liquely spreading stem-leaves, the angle formed with the stem 
being about 60 degrees; in the presence of rhizoids on its lobules; 
and in the apices of the lobules of its stem-leaves, which are obtuse 
or subacute instead of being rounded. The leaf-cells are much 
the same in the two species, both in size and in the characteristics 
of the cell-walls. 
A still closer ally is the recently described R. prolifera Arnell,* 
known only from the type specimen, which was collected in 1898 
by H. Nilsson-Ehle at Bulkur, in the valley of the Lena, Siberia. 
Through the kindness of Dr. Arnell the writer has been enabled 
to compare a portion of this type specimen with the material of 
R. polyclada and finds that, in spite of their close relationship, the 
two species cannot be considered synonymous. 
In R. prolifera the branching is usually just as copious as in 
R. polyclada, and there seems to be an equal lack of rhizoids; the 
branches, however, are of a somewhat different character. A 
very small number are essentially like the main stem, their leaves 
resembling the stem-leaves in all essential respects; but the vast 
majority are more nearly comparable with the small-leaved 
secondary branches of R. polyclada, except that they are shorter 
and more often subdivided. They represent the “flagella” of 
Arnell’s description and possibly act as propagula in multiplying 
the species vegetatively. The stem-leaves of R. prolifera differ 
from those of R. polyclada in having a less arched or even straight 
keel, a scarcely evident indentation at the end of the keel, a more 
sharply pointed and differently shaped lobule (the outer margin 
being only about half as long as the inner margin), and sometimes 
* Ark. for Botanik 132: 12. pl. 1, f. 2.2. 1913 
