14 H. C. BOLD 



vidual, probably through no fault of his own, is apparently un- 

 aware that the appearance of the chromatophore of algae varies 

 markedly under different physiological conditions, a fact clearly 

 emphasized by Czurda (1935) and verifiable by continuous study 

 of algae in cultivation. 



Perhaps these remarks and examples may serve to emphasize 

 the author's studied opinion that phycologists, insofar as many 

 of their investigations of lower algae are concerned, are at about 

 the stage of the early bacteriologists who confidently described 

 new species of bacteria on the basis of morphological criteria 

 alone. A similar situation exists in the fungi as a result of activi- 

 ties by some of our mycological colleagues especially those in 

 medical mycology. There is, however, an optimistic aspect of this 

 problem: in many cases, bacteria and dermatophytes fail to pro- 

 vide sufficiently distinct morphological criteria for the recognition 

 of the individual forms or species. Even in such difficult algal 

 genera as Chlamydomonas, Chlorococcum, Chlorella, and many 

 soil algae, careful, prolonged and repeated observation of the 

 organisms maintained in laboratory cultures usually reveals suf- 

 ficienly clear morphological criteria to effect species-differentia- 

 tion. It well may be that further work in such genera, particu- 

 larly Chlorella, will indicate that the solution of the taxonomy 

 of these forms must be based to some degree on physiological 

 criteria obtained from their study in pure culture. 



The problem of segregating such genera as Chlamydomonas, 

 Palmella, Gloeocystis and Gloeococcus and other Tetrasporalian 

 forms has been mentioned previously. Comparative cultural 

 studies under controlled conditions correlated with field observa- 

 tions will, in the* author's opinion, more rapidly provide a satis- 

 factory solution than examination of countless herbarium speci- 

 mens. The crux of die problem here is the degree and duration 

 of motility as well as structure and manifestation of the gelat- 

 inous layers in which the cells are encapsulated. The extent to 

 which the external environment is responsible for evoking these 

 diagnostic criteria has never been adequately investigated. 



Most of these genera of Chlorophyta yield readily to cultiva- 

 tion. The unicellular Chrysophyta (Chrysophyceae) and Pyrrho- 



