480 Evans: THREE SOUTH AMERICAN SPECIES OF ASTERELLA 
In the structure of the thallus, in the restriction of the sexual 
organs to ventral branches, and in many of the characters derived 
from the female receptacles and the spores, A. boliviana shows a 
close relationship to A. elegans and especially to A. lateralis. It 
differs from both of these species in the broader and usually longer 
appendages of the ventral scales, which are usually much more 
abruptly contracted into an apical cilium and which are further 
distinguished by shorter cells and by the frequent occurrence of 
cells with oil-bodies. In the basal portions of the scales the cells 
with oil-bodies are unusually abundant, numbering at least twice 
as many as in A. elegans and often five to ten times as many. The 
elaters of A. boliviana, moreover, usually show two spirals at the 
ends, while those of A. elegans and A. lateralis usually show only 
one. 
In distinguishing A. boliviana from A. elegans further charac- 
- ters of importance may be drawn from the sexual branches, the 
androecia, and the female receptacles. In A. boliviana the sexual 
branches (so far as known) are invariably short; the antheridia 
form a vaguely defined group without marginal paleae; and the 
female receptacle is covered over with very short tubercles, 
scarcely apparent in the central portion: in A. elegans the sexual 
branches vary greatly in length; the antheridia are in a clearly 
defined and elevated group, surrounded by marginal paleae; and 
the female receptacle is hemispherical in the center and covered 
over with longer and more conspicuous tubercles. Some of the 
characters which separate A. boliviana from A. elegans are shared 
by A. lateralis, but aside from the important differences derived 
from the ventral scales and elaters certain other differences derived 
from the spore markings deserve mention. In A. Jaéeralis, 
except for the coarse reticulum, the spore surface is covered over 
with crowded and minute dots but not with lines; in A. boliviana 
the surface shows both dots and lines, the latter sometimes 
anastomosing and thus forming secondary reticula within the 
meshes of the coarse reticulum. 
SHEFFIELD SCIENTIFIC SCHOOL, 
YALE UNIVERSITY, 

