32 



ARKIV FÖR BOTANIK. BAND 12. N:0 9. 



in Sorolpidium and Pyrrliosorus at the formation of the zoo- 

 spores, the resemblance with the Plasmodiophoraceae becomes 

 still more conspicuous. — The contents of the sporangia (the 

 walled amoebae) in one form and a collection of spore-mother 

 cells in another must surely be considered homologous; 

 whether a surrounding wall is formed or not must be con- 

 sidered of minor importance — and whether it by the divi- 

 sions enters the daughter-cells. . 



Plasmodiophoraceae. 



Zoospore- 



I 

 Myxoplasma 



Xo membrane 



Spore-mothercells 



Formation of 



(4) spores enclosed 



by a membran 



I 



Aggregations of spores 



I 

 Swarming of the zoo- 

 spores ('sometimes pro- 

 bably after further 

 divisions) 



Pyrrliosorus. 



Zoospore. 



I 



Mj'^xoplasma 



Formation of an 

 enclosing membrane 



Spore-mothercells 



Aggregations of 

 spore-mothercells 



Formation of 

 (8) zoospores 



Swarming 



Sorolpidium. 



Zoospore. 



I 

 Myxoplasma 



Formation of an 

 enclosing membrane 



Spore-mothercells 



Aggregations of 

 spore-mothercells 



Formation of 

 (2 — 4) zoospores 



Swarming 



Closer cytological investigations of Crysophlyciis, Astero- 

 cystlSy Rhizomyjcoi and Woronina will probably prove that 

 these forms have much in common with Pyrrhosorus . How 

 much, we are not yet able to determine. 



As regard« the Plasmodiophoraceae it would be of great 

 interest to ascertain how the germination of the spore takes 

 place. We are of opinion that it must be assumed that 

 swarming-spores are formed which copulate and produce a 

 small myxoplasma which actively penetrates the epidermal 

 cells of the host-plant — both as regards the parasitic species 



