Evolution of Plants 307 



which appears as refractive masses within it. But alongside 

 these in some genera, and embedded in the colorless central 

 protoplasm, are often small refractive bodies that behave to 

 stains, digestive agents, and chemical substances as does chro- 

 matin material. Such seems to be closely related to the chlor- 

 ophyll bodies, and even united with them by fine threads, 

 while they suggest the diffuse beginnings of nuclear chromatin, 

 which, it should be emphasized, are early associated with 

 the chromatophore on the one hand and with the central proto- 

 plasm on the other. 



In the higher or thread forms of the Cyanophycese, glycogen, 

 albumen masses, and protein granules may all be present in 

 the chromatophore, or may be stored — often at opposite ends 

 of each cell — in the central protoplasm. But they further 

 show an increasing formation of chromatin granules in the 

 central protoplasm, which, instead of being loosely connected 

 by fine threads as at first, gradually unite into granular loops 

 or wreaths, which occupy a considerable part of the central 

 area in Oscillatoria and Cylindrospermum. Such represent, 

 as most recent observers have accepted, a developing but still 

 diffuse state of the cell nucleus in higher plants. And it should 

 here be emphasized that the refractive chromatin granules 

 of the chromatophore, and those of the evolving nucleus, seem 

 always to be connected by delicate threads, that act as an 

 elastic connecting substance between the protoplasm and 

 chromatin. 



As regards the pigment of the chromatophore, this may 

 vary, even in one genus like Pleurocapsa from yellow to olive, 

 then to blue-green and violet, in Dermocarpa from violet-pink 

 to rose-red, in Plectonema from light green or yellow-green 

 through blue-green and pale red to rose-colored. This pig- 

 ment has been called phycocyan, and spectroscopically is 

 allied to phycophsein that is typical of the brown seaweeds, 

 and phycoerythrin that is typical of the red seaweeds. By 

 transmitted light it is of a rich blue color, but in mass it ex- 

 hibits a carmine-red fluorescence. 



Now from the spectroscopic researches of Engelmann {112: 

 1) and Gaidukov {113: 484, 517) we learn that the color of 

 blue-green and of other algse varies according to the law of 

 "complementary chromatic adaptation," and even in one 

 genus like Oscillatoria threads may become green in red light, 

 blue-green in yellow light, pink to red in green light, and bro\\'n- 

 yellow in blue light. Such results accord with the observations 

 that red algse occur in the deepest marine zones (20-500 ft.) 

 where mainly blue-green rays penetrate; that the brown and 



