PHYCOMYCETES 



137 



upon plants growing in moist situations. A motile spore, zoo- 

 spore, comes to rest upon an epidermal cell, and penetration 

 doubtless results after a minute perforation is made, by the 

 streaming through of the protoplasmic body. There are no evi- 

 dences of a mycelium. The presence of the parasite in the 

 epidermal cell may in time cause a minute gall-like abnormality 

 of the host. The small galls are sometimes so numerous as to 

 give the host the appearance of being affected by a rust fungus. 



Fig. 41. Synchytrium on Puerarta, Stages in the For- 

 mation OF THE POLYNUCLEATE FUNGOUS BODY AND THE 



Lysigenous Cavity. (After Kusano) 



The simple protoplasmic mass resulting from the growth of the 

 penetrating swarm spore becomes either a fruit body, sorus, or 

 a resting spore ; in the latter case it becomes a fruit body ulti- 

 mately, and this, at maturity, breaks up into numerous sporangia, 

 and may therefore be termed a sorus, each sporangium eventually 

 producing swarm cells. 



Harper has studied from a cytological point of view the de- 

 velopment of Synchytrium decipiens Farl., and from this study 

 may be distinguished seven more or less distinct stages in the 

 life cycle of this organism : (1) after the swarm spore comes to 



