550 THE PATHOGENIC ALGAE. 



The zoospores (gametes) copulate in the gelatinous mass which 

 escapes, and break out from it as free swarming zygozoospores. 

 When the Zemna falls to the bottom in autumn, or when it 

 dries up, the cells of the alga become resting-cells capable of 

 sustaining drought. Plants of Lemna seem to be little 

 disturbed by attacks of the endophyte, and develop their 

 flowers normally. 



Chi. Knyanuin Kirch n. Frequents Lemna minor and L. gibba, 

 Ceratophyllum demersum, Elodea canadensis, but not Lemna 

 trisulca. It forms zoospores only, and these on penetrating 

 into a host do not produce a cellulose button like the species 

 just described. They appear to be able to enter the host only 

 by the stomata. 



ChL pallidum Klebs. Grows in the intercellular spaces of 

 Lemna trisulca. 



Chi. viride Schroet. Found in the respiratory cavity of 

 Rumex obticsifoUus. 



Other species occur in dead Phanerogams or in Algae. 



Stomatochytrium lininan- 

 themam Cunningh. Inhabits 

 the respiratory cavity of leaves 

 of Limnanthemum indicum in 

 India. 



Chlorocystis Cohnii Eeinh. 

 Occurs as a " shelter-parasite " 



Fig. 326. — £7ido^j>ftacra biennis in Potamogeton jjj marine al^^aC. 

 luce-Hi. Cell of the Alga, which has penetrated ^ 



through the epidermis a few weeks previously. SCOtillOSphaera paradOXa 



Klebs. Found between the 

 cells of dying leaves of Hypnum and Lemna triscida. 



Endosphaera biennis Klebs. The zygozoospores have four 

 cilia, and swarm in water till they reach a living leaf of 

 Potamogeton lucens. They generally come to rest on the under- 

 side of a leaf at the boundary wall between two cells, and 

 become invested in a membrane. A process is next sent in 

 between the epidermal cells, and all the cell-contents pass over 

 into it, the outer portion dying away. The young alga now 

 makes its way into the intercellular spaces of the sub-epidermal 

 tissue and becomes a resting spore. In spring this spore 

 gives off biciliate gametes, which, after copulating, become 

 zygozoospores. This shelter-parasite has not yet been observed 



