.Ian., 1910.] Munochytrium, a New Genus. 49 



mine their behavior and their structure, particuhirlv 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 Ch}'tridiales thev are very vari- 

 able for one finds in genera undoubtedly closelv related great 

 diversity in this regard. The zoospores of Synchvtrium for 

 example have one flagellum while those of Woroninella have 

 two. The behavior of the zoospores of some of the Chvtrids 

 goes to show that the flagella of this group may be of verv 

 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 ver}' 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 highlv 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 typical flagellate zoospore 

 than those of other Chytrids. For it seems probable from the 

 habits of the ftmgus that the motile organs of Monochvtrium 

 spores are verv inefficient as compared with those of the Svn- 

 ch}' tria. 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 widely 

 distributed over the plant and seldom so excessivelv abundant as 

 Monochytrium. This is especially 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 much as 

 one percent of the young stages that he has in Monochytrium. 

 The reason is that the parasites are so much more widelv[scattered 

 that their detection when very small is difficult. Nevertheless, 



