256 University of California Publications. [Botany 



the subject in which the views on each structure and process are 

 brought together. 



All three workers agree in calling the "central body" a nu- 

 cleus, and Kohl and Phillips agree that it may enter upon a state 

 of rest, though Kohl thinks this is very rare, while Olive finds it 

 in continuous mitotic activity, except in spores and heterocysts. 



Structure of the Nucleus. 



Kohl. The nucleus is composed of a ground substance, ' ' Cen- 

 tralkorner," and chromatin. 



Phillips. The "central body," the nucleus, is composed of 

 chromatin (p. 325, first conclusion) and a "finely granular 

 ground substance" (p. 284). 



Olive. The ' ' central body, ' ' the nucleus, ' ' consists of a more 

 or less dense, fibrous achromatic portion," and "a number of 

 minute globular, or somewhat irregularly shaped chromatin gran- 

 ules" (p. 35), and sometimes central granules. 



The Ground Substance. 



Kohl. The ground substance sends out radiating threads to 

 the cell-wall. 



Phillips. The granular ground substance permeates the nu- 

 cleus and sends out finely granular kinoplasmic-like processes 

 through the " chromatophore, " which pass out to the cell-wall 

 and form the central part of the "protoplasmic ciliary-like 

 growths" (p. 284), and actually pierce the cell-wall, and "cause 

 the movements of the trichomes" (p. 326). 



Olive. The shape of the ground mass varies with the shape 

 of the nucleus. 



Chromatin. 



All three agree that chromatin is present in the nucleus of the 

 Cyanophyceae, but of the form it assumes and of its behavior the 

 following is said : — 



Kohl. "Wie jeder Zellkern, so enthalt auch der Zentral- 

 korper der Cyanophyceen Substanz, welche sich gewissen Far- 

 bungsmitteln gegenuber anders verhalt, als die Grundmasse des 

 Zentralkorpers. Da diese sich distinkt farbende Substanz sich 



