PLASMODIOPHO RALES 



769 



A 



B 



F 



D 



i j 





_j 



I 



Fig. 57. Polymyxa graminis Ledingham in roots of wheat 



A. Free-swimming zoospore with a long and a short flagellum, both of 

 which are here directed anteriorly. B. Zoospore immediately after release. 

 C-D. Shapes assumed by zoospores during amoeboid movement; fiagella have 

 now been lost. E. Septate thalli, some segments of which have become con- 

 verted into zoosporangia; each sporangium bears a discharge tube which 

 reaches the outside medium. F. Naked myxamoebae during active vegetative 

 growth; it is in such thalli that the nuclei divide by protomitosis. G. Meronts 

 formed by division of myxamoebae. H. Same meronts coalesced. /. Myxa- 

 moebae just prior to segmentation into resting spores. J. Spore clusters begin- 

 ning to be formed from myxamoebae. (Ledingham, 1939) 



the precise relationships of the Plasmodiophorales, admitted to their 



"closer affinity with the simple fungi than was formerly believed to exist." 



Unfortunately, the whole group still so urgently requires a thorough 



study that no significant account of the aquatic species, save for the 



