Vol. 2] Gardner. — Cytological Studies in Cyanophyceae. 247 



and their action on the living material noted. Loeffler's methy- 

 lene blue was used first, and it was soon discovered that while not 

 all the Cyanophyceae cells are alike in cytological -characters, 

 one feature of their reaction to stains seems to be common to all, 

 viz., that the central part of the cell uniformly has a stronger 

 affinity for stain than other parts. The central part in many 

 species will be intensely colored even before the cytoplasm 

 through which the stain has to pass is colored. Most specific 

 chromatin stains act in the same way. This leads to the belief 

 that chromatin may be present in this part of the cell. But by 

 this method alone differentiation is not sufficient to enable one to 

 determine the form in which it exists, for very soon other cell- 

 organs become colored, and the whole protoplast becomes dif- 

 fusely stained. The method afterward employed was to "over- 

 stain, ' ' and then to remove the superfluous stain and dissolve out 

 that which seems to be held mechanically or in loose combination, 

 observing which parts of the cell give it up first. It was found 

 by this method that the central part of the cell is uniformly the 

 most tenacious of chromatin stains. It was further found that 

 the central part is not homogeneous. The whole mass does not 

 equally become fainter as the stain disappears, but certain parts 

 resist the action of the solvent a long time. In most species thus 

 stained it was found that the granules were the last to give up 

 the stain. Much variation exists among the species as to the de- 

 gree of differentiation of the central part, and it was not a simple 

 matter to determine at first what is typical. Pursuing the method 

 of staining intra vitam, I finally came across Symploca Musco- 

 rum, which, although having quite a thick sheath, has a very 

 strong affinity for aqueous methylene blue; and in this, as in 

 other species, the central part takes the stain first. Furthermore, 

 the action is almost instantaneous. Staining on the slide with 

 aqueous methylene blue, dehydrating, and mounting in balsam 

 may be accomplished within 5 minutes, with a most excellent dif- 

 ferentiation of the central part of the cell. The granules stain 

 red and are scattered within and around the mass of branched 

 thread-like structures which stain blue, while the surrounding 

 cytoplasm remains bluish or greenish, according to the degree of 

 washing out of the stain. In this species was found something 



