39 



2. in rich feeding solution (water + salts + peptone + glu- 

 cose) vigorous growth of green algae takes place. 

 C. Chlorococcum iufusionum from the Lichen Xanthoria pa- 

 rietina. 



a. h. when cultivated in light or in darkness and in all kinds 

 of feeding solutions the algae remain green. 



So the algae j^rove to become colourless under very different 

 conditions as to light and food. Therefore we ought to examine, 

 if perhaps our symbiotic algae can lose their green colour and 

 pass into the colourless form by a comhination of darkness (or 

 light) and a certain feeding milieu. And at the same time we 

 should examine, if the colourless form of the symbiotic algae may 

 in its turn pass into the green one by a certain combination of 

 light (or darkness) and feeding milieu. 



For the present I will treat the first question. We have to 

 examine then, to which of the following types of algae — the 

 only ones possible and partly hypothetical — our symbiotic 

 alga belongs : 



A. when cultivated in darkness, 

 type I (Scenedesmus). 



in poorer feeding solution the algae remain green, 

 in rich feeding solution the algae become colourless, 

 type II (Chlorella, Stichococcus). 



in poorer feeding solution the algae become colourless, 

 in rich feeding solution the algae remain green, 

 type III (Chlorococcum from Xanthoria). 

 in poorer feeding solution 



the algae become colourless. 



„ _ , , , the algae remain green. 



in rich feeding solution ' 



type IV (hypothetical). 



in poorer feeding solution 



in rich feeding solution 

 B. when cultivated in light, 

 type I (Scenedesmus). 



in poorer feeding solution the algae remain green. 



in rich feeding solution the algae become colourless. 



