OKDER PLASMODIOPHORALES 



31 



emerging from the cysts are nonflagellate in Lahyrinthula and anteriorly 

 uniflagellate in the possibly related Lahyrinthomyxa. (Fig. 6.) 



Order Plasmodiophorales. This order to which eight or more genera 

 have been ascribed is not definite as to its hmits or relationships. The 

 type genus Plasmodiophora differs in so many points from many of the 

 genera assigned to the order that it may be necessary to limit the order 





Fig. 6. Labyrinthulales. Lahyrinthula 7nacro- 

 cystis Cien. (A) "Net Plasmodium," showing 

 clumps of cells on the "tracks" and cells sending 

 out threads which are the beginnings of new tracks. 

 (B) Highly magnified single cell lying on track. 

 (Courtesy, Young: Am. J. Botany, 30(8) :586-593.) 



to one genus and to place the others in another order, perhaps not at all 

 closely related. The type species P. hrassicae Wor., causing swellings and 

 malformations of the roots of Brassicaceae (Cruciferae), will be discussed 

 first and then some of the others with remarks as to their differences and 

 possible relationship. Woroni7ia, placed here by Sparrow (1943), is re- 

 turned to a position in the Order Lagenidiales because of its cellulose 

 walls and the possession of flagella of two types. Possibly other genera 

 may have to be relegated to that position also. In the following account 

 many points still are disputed or assumed without adequate confirmation. 

 The spores of Plasmodiophora hrassicae possess a dark wall which, 

 according to van Wissenlingh (1898), contains chitin but not cellulose. 

 Upon germination, usually a single zoospore emerges, although Honig 

 (1931) and Rochlin (1933) claim that only a nonflagellate amoeba is 



