66 
Mycologia 
permanently. These authors describe and figure oospores similar 
to those of P. erythroseptica, but considerably larger, and agreeing 
in all respects with those described by Clinton. As the antheridia 
and oogonia were found to be of the same peculiar type as those 
of P. erythroseptica the authors are led to designate Clinton’s 
“ superimposed oogonial thread ” as a defective observation of 
the material in hand. “No spores were observed resembling in 
any way the resting spores with protuberances on their walls 
figured by Jones, and recalling Artotrogus hydnosporus.” Ac- 
cording to the observations of these authors when a culture once 
begins to form sexual organs,” it continues to do so in the sub- 
sequent transfers without intermission ; and although the relative 
abundance of these bodies may vary somewhat in the successive 
cultures, as a rule, the subsequent transfers from cultures rich in 
oogonia, become themselves in due time, also well provided with 
them.” Several transfers covering a period of some fifteen 
months from the time of isolation appear to have been necessary 
for the formation of the oosporic habit, while about a week is 
necessary after making the transfer for the sexual organs to 
appear in the subculture. It is still an open question as to the 
conditions under which oospores occur in nature, if they do so at 
all. A double oospore is figured by these authors, and something 
approaching closely to such a condition is figured by Clinton. 
Among the most interesting experiments recorded by Clinton 
^1911 b: 771-773) are those which concern the attempted hybrid- 
ization of species. In these the first attempt was made with cul- 
tures of P. infestans and P. Phaseoli, the latter being the more 
vigorous species of the two and producing oospores most abun- 
dantly. When these species were sown in the same culture “ we 
obtained oogonia, usually only in the vicinity of the P. infestans 
colony, which were entirely different from the normal oogonia of 
P. Phaseoli that were produced abundantly all through the culture. 
These different oogonia were of the P. infestans type, which at 
that time we were just beginning to get in a small way in our pure 
cultures of P. infestans on oat juice agar, and they differed in 
that they usually produced mature oospores, and were far more 
abundant than we have ever obtained them in pure cultures of P. 
infestans. . . . They also differ, perhaps, in not being so deeply 
