PHTLOGENY OF CHYTRIDIALES AND VEGETATIVELT SIMILAR FORMS G31 



nidiales, and Peronosporales. Since, however, Ellison (1945) has shown 

 that the two flagella oi Plasmodiophora are both of the whiplash type while 

 those of the other groups assigned to the Biflagellatae have one each of the 

 tinsel and whiplash type, the relationship of Plasmodiophora appears more 

 likely to be with the biflagellate slime molds whose flagella are both of the 

 whiplash type and whose plasmodial structure is more nearly similar. 

 Whether the other genera at present assigned to the Plasmodiophorales 

 really belong there needs further study, especially of their flagellar 

 structure. 



The nonflagellate order Acrasiales is possibly closely related to the 

 true slime molds. Besides the loss of fiagellum production there is no 

 definite peridium nor is a capillitium produced unless possibly the slime 

 in which the spores are embedded and which helps to make up the growing 

 stalk are modifications of these structures. Furthermore the production of 

 true Plasmodia is lost except possibly just before spore formation, but 

 sexuality appears to be present (Skupienski, 1920). As for the Labyrinth- 

 ulales it can only be surmised that they possibly are related to the Myce- 

 tozoa because of their naked cells, which form a sort of pseudoplas- 

 modium, and the encystment of their spores. Their life history is so 

 incompletely known that their relationship cannot be determined more 

 closely at present. 



Phylogeny of Chytridiales and Vegetatively Similar Forms 



The whole group of chiefly aquatic fungi formerly grouped together 

 under the name Chytridiales agrees in the production of flagellate naked 

 swarm cells which eventually encyst and enlarge and become the spo- 

 rangia or give rise to the sporangia within which the swarm cells are pro- 

 duced. The study of the number, location and structure of the flagella has 

 shown that this group must be divided into at least three orders : Chytri- 

 diales (in the more limited sense), with one posterior whiplash fiagellum; 

 Hj^phochytriales, with one anterior tinsel type fiagellum; and certain 

 families of the Lagenidiales, with two anteriorly or laterally attached 

 flagella, one of the tinsel type (directed forward if the flagella are laterally 

 attached) and the other of the whiplash type (directed posteriorly in most 

 cases). Correlated with these flagellar characters are chemical differences 

 in the composition of the cell wall. In the Lagenidiales this gives the 

 cellulose test readily with chloriodide of zinc, in the Hyphochytriales this 

 reaction may or may not appear and may depend upon the age of the 

 organism, while in the Chytridiales only rarely is cellulose revealed by 

 this test and in some cases fungus chitin occurs. 



In 1942, the author suggested that these three orders which vege- 

 tatively and in their mode of reproduction are so closely parallel, might 

 have had a common origin in some of the green, heterocont, one-celled, 



