CHLOROCOCCALES 



37 



* 



Chlorococcaceae : Chlorochytrium (chloro, green; chytrium, 

 vessel). Fig. 27. 

 The swarmers, which may either be zoospores or motile zygotes, 

 settle on the leaves of aquatics, principally species of Lemna 

 {Chlorochytrium lemnae), whilst another species is also known which 

 penetrates the leaves of Polygonum lapathifolium. Tubular pro- 

 longations grow out from these attached bodies and enter the host, 

 either by way of the stomata or else between two epidermal cells. 



B 



e<: 



Fig. 27. 



Fig. 26. Characium angustatum. A, vegetative cells ( x 650). B, cell commencing 

 zoospore formation ( x 650). C, liberation of zoospores: the cell is probably- 

 broken accidentally ( x 650). (After Smith.) 



Fig. 27. Chlorochytrium lemnae. A, entrance of zygote into host. B, resting 

 cells in leaf of Lemna. C, resting cell. (After Fritsch.) 



Subsequently the end of the tube swells out into an ellipsoidal or 

 lobed structure into which the contents of the swarmer pass. These 

 swellings, which are to be found in the intercellular spaces of the 

 host's tissues, become rounded off, and in the autumn sink down 

 with the Lemna fronds to remain dormant until the next spring. In 

 Polygonum the swollen filaments even crush the host cells which 

 may become partially dissolved. In the spring the cell contents 

 divide up into biflagellate swarmers, which are probably haploid, 

 and these are liberated all together in a mucilaginous vesicle. 



