KING: CYTOLOGY OF ARAIOSPORA FULCHRA. 
215 
very few zoosporangia are found, although on many plants a few 
empty ones may be seen projecting beyond the region where the 
oogonia are collected in great numbers. Within these oogonia are 
developed in a few weeks or even less time, thick walled oospores 
that later fall to the bottom of the pond as resting spores. Although 
the further history of these resting spores is wholly unknown, there 
is some reason for believing that they rest until early the next sea¬ 
son before germinating. 
In the first part of May, the formation of oogonia and antlieridia 
is practically suspended ; throughout the remainder of the season 
the plants are propagated chiefly by means of zoosporangia and 
zoospores. One would naturally infer from this asexual propagation, 
which is carried on to a limited extent until fall, that thick walled 
oospores would be produced in great abundance at this time in 
order to tide these plants over the winter. 
As a matter of fact no such spore formation took place in the 
ponds visited during the season of these collections. This fact is 
given particular emphasis because the writer was extremely anxious 
to secure material showing young stages in the development of the 
oogonia and was forced to wait until the next April in order to get 
it. A possible explanation of this early oospore formation, sug¬ 
gested by its aquatic habit, is that the plant has fully as much diffi¬ 
culty in persisting through the summer as in withstanding the 
unfavorable conditions of winter. For in summer many ponds 
entirely disappear and almost all are greatly reduced in area, thus 
exposing the plants about their edges to long periods of drought. 
Such an explanation assumes, of course, that the oospores of one 
year do not germinate until the following spring. Few positive 
details are known in regard to the germination of the oospores. 
It is known, however, that they fall from the oogonium at the end of 
a couple of weeks — too soon to get their later cytological history. 
Even in this short time, nevertheless, each oospore has built a thick 
wall, the food material has collected into one or more conspicuous 
globules and almost all traces of the fine meshed, central ooplasm 
have disappeared. 
