Jan., 1910.] 
Monochytrium, a New Genus. 
49 
mine their behavior and their structure, particularly the char- 
acters of their organs of locomotion. For it will be recalled that 
while in many groups the number and position of the flagella are 
so constant as to be made the basis of distinctions of ordinal 
or of even higher rank, in the Chytridiales they are very vari- 
able for one finds in genera undoubtedly closely related great 
diversity in this regard. The zoospores of Synchytrium for 
example have one flagellum while those of Woroninella have 
two. The behavior of the zoospores of some of the Chytrids 
goes to show that the flagella of this group may be of very 
indefinite organization. Atkinson has shown that when lib- 
erated inside the sporangium the zoospores swim actively 
forward until they strike the wall of the sporangium when 
the flagella are retracted and the zoospore puts out pseu- 
dopodia by which it gropes for the opening of the spor- 
angium. In case it is located too far from the ostiole to 
reach it with its pseudopodia it resumes its flagellate form and 
swims about again until it finally escapes. Such behavior indi- 
cates very plainly that the flagella of these zoospores resemble 
the long actively lashing pseudopodia present in such of the 
Protozoa as Mastigamoeba more than the definite highly special- 
ized motile organs of the Protococcoid forms. In the latter 
group the zoospores have no power of retracting and again put- 
ting forth their flagella but retain the same ones throughout 
their active stage. Comparisons of flagella based on analogies to 
the highly specialized organs of other groups must obviously be of 
somewhat doubtful value. 
Indications are not lacking that the spores of Monochytrium 
are even more widely different from the tvpical flagellate zoospore 
than those of other Chytrids. For it seems probable from the 
habits of the fungus that the motile organs of Monochvtrium 
spores are very inefficient as compared with those of the Syn- 
chytria. In each area where it has been found the abundance of 
the individual parasites was very great. At the same time the 
infested areas are narrowly circumscribed. This is in strong 
contrast to the habit of Synchytrium which is always widelv 
distributed over the plant and seldom so excessively abundant as 
Monochytrium. This is especiallv evident when one considers 
the young stages of the parasite. Such a complete series of young 
stages as here figured for Monochytrium would be exceedinglv 
difficult to assemble for any species of Synchytrium with which 
I am familiar; in very much more extensive work with Synchyt- 
rium decipiens in all stages the writer has never seen so muchffis 
one percent of the young stages that he has in Monochytrium. 
The reason is that the parasites are so much more widely scattered 
that their detection when very small is difficult. Nevertheless, 
