196 MINNESOTA BOTANICAL STUDIES. 



dermal cells. The membrane of this tube becomes thickened 

 by subsequent layers, the tube swells with the absorption of the 

 chlorophyll and protoplasm and the intercellular endophyte 

 results, with a cellulose button protruding from the point where 

 the germinating tube entered. The endophyte then becomes 

 pyriform and almost opaque on account of the density of the 

 chlorophyll. By free cell formation large cells are formed in 

 the endophyte and these finally break into a large number of 

 zoospores which are expelled through the cellulose protuber- 

 ance from the nurse-plant epidermis. The endophyte is, there- 

 fore, an independent organism closely related to Hydrocytium 

 (Characium A. Br. ) on the one hand and to Synchytrium on 

 the other. With the Eu-Synchytrium group its cell form and 

 the formation of zoospores by a preliminary division into seg- 

 ments, corresponding to the zoosporangia of Synchytrium, 

 agree, but it differs in the presence of chlorophyll and of a 

 germination tube and in its intercellular position. Upon these 

 observations Cohn founded the genus Chlorochytrium and de- 

 scribed it as follows : 



Planta endophytica viridis unicellaris, globosa ovoidea vel 

 irregulariter curvata bi, tri, multiloba dense conferta plasmate 

 viridi, primum in segmenta majora diviso dein secedente in 

 zoosporas immersas pyriformes virides processibus tubulosis ex- 

 tus emissas. 



Chlorochytrium lemna upon which the genus is based is then 

 described. 



Cohn pronounces Chlorochytrium a true parasite. That no 

 deleterious effects upon the host are visible is paralleled in Per- 

 onospora and Synchytrium. In its intercellular position it re- 

 sembles the Uredineae. 



Two years after Cohn's observations were published Kny 

 described a new species of Chlorochytrium endophytic upon 

 Ceratophyllum demersum. It differs from Chlorochytrium 

 lemnce in size and in the absence of a cellulose button. 



In 1877 Wright established a third species of Chlorochy- 

 trium, C. cohnii Wright. 



" The zoospores impinging on the fronds of several species 

 of marine algae quickly assuming a figure-of-eight form, the 

 lower sphere growing into the frond and rapidly assuming com- 

 paratively large dimensions, the upper sphere remaining as a 

 tube-like neck portion to the larger mass. On the cell arriving 



