290 Phillips on a Comparative Study of the 



Cohn (16) discussed at some length the coloring material 

 of the Cyanophyceae, but did not deal with the question of 

 the chromatophore. Hie found a green coloring substance 

 which was soluble in alcohol, and which he considered to be 

 chlorophyll, and a blue pigment which he termed phycocya- 

 nin which was soluble in water. Naegeli had termed the 

 light green pigment phycochrome, and when the bluish 

 tint was present he called it phycocyan, this latter being 

 synonymous with the phycocyan of Kutzing. Evidently 

 therefore the phycocyan of Nageli was a compound of the 

 two pigments mentioned by Cohn, and the name phycocyan 

 should properly belong to the simpler substance as applied 

 by Cohn. A third pigment, phycoxanthin, was met with 

 by the latter observer in those forms of the Cyanophyceae 

 which have the purple color. This he found to be a modi- 

 fication of the phycocyan, differing very little from the blue 

 variety. Hansgirg found that the pigments of the Cyano- 

 phyceae had the power to elaborate food without the pres- 

 ence of light, but whether this was due to the phycocyan, 

 he does not say. Certainly it cannot be due to the chloro- 

 phyll alone. It would be of interest to know if the recently 

 discovered Roentgen rays, or any similar cause, could be 

 active upon the chlorophyll when the phycocyan is present. 

 Molisch (55) demonstrated that the phycocyan was a crys- 

 talline albuminous body, easily recognizable in plants fixed 

 in a solution of cupric sulphate. Warming (80) considered 

 that there was no chromatophore except possibly in a few 

 forms such as Glaucocystis where it might be slightly devel- 

 oped. Zacharias could not determine its presence because 

 he could not see a bounding membrane. Crato (19) found 

 a sharply defined chromatophore, having an amoeboid-like 

 form, and with thick stratification. Zukal (103) thought 

 that a highly organized chromatophore was usually lacking, 

 though he was able to determine a thin utricle-like layer of 

 clear protoplasm between the colored crust and the cell wall. 

 Nadson (57) considered the whole colored protoplasmic 



