38 



phyll in darkness (Heinricher (27) 1883, Etard and Bouilhao 

 (19) 1898; Matruchot and Molliard (43) 1900; Oltmanns (47) 

 1905). Moreover, the same is known about the seedlings of some 

 Gymnospermae, about ferns and mosses (Stahl (55) 1909). 



So we have to find another explanation for the facts, men- 

 tioned above (p. 35), than the simple one given by Lankester 

 and Brandt (p. 36—37). 



Consulting the botanical literature I found, that in algae the 

 producing or not-producing of chlorophyll — in darkness and 

 even m light ! — depends for a great deal on the nature of the 

 feeding-milieu (Beijerinck (4) 1890; Artari (2) 1902; Grint- 

 ZESCO (24) 1903; Radais (50) 1900). But a rule in general 

 appliable cannot be given for it, one kind of alga behaves in 

 this way, another in that way. By combining the results of 

 the investigators mentioned we may, for instance, distinguish the 

 following 3 types of algae: 



A. Scenedesmus. 



a. when cultivated in light. 



1. in water + salts + N H^ N O3 without organic sub- 

 stances no growth talses place (Sc. acutus) or vigorous 

 growth of green algae (Sc. caudatus). 



2. in water + salts + little organic substances growth of 

 green algae takes place. 



3. in rich organic feeding solution the algae become colourless. 

 h. when cultivated in darkness. 



1. when glucose is present in the solution growth of green 

 algae takes place. 



2. in rich organic feeding solution the algae will probably 

 also become colourless. 



B. Chlorella vulgaris, Stichococcus bacillaris. 

 a. when cultivated in light. 



1. in poor or in rich feeding solution growth of green 

 algae takes place. 

 h. when cultivated in darkness. 



1. in poorer feeding solution (water + salts -f K N O3 + 

 glucose) the algae become colourless. 



