Cytology and Movements of the Cyanophycew. 279 



Ordinary preparations were made by taking the unstained 

 or stained organisms and carefully spreading them out on a 

 slide in water or whatever medium was to be used for the 

 examination. For filamentous forms, such as Oscillaria, 

 this could easily be done by dropping the mounting medium 

 upon the organisms on the slide, thus the individual trich- 

 omes would be separated, while, if in a pellet of jelly as in 

 the case of Nostoc, the gelatinous mass was placed on a slide 

 and carefully pressed out in the selected medium, when the 

 trichomes would be plainly shown. In mounting, several 

 methods were followed. Two per cent, acetic acid gave 

 very good results and permitted the finest structures to be 

 brought out. This acid also swelled some parts slightly and 

 made some structures more visible though obscuring others. 

 Another method was to mount in weak glycerin. This also 

 gave satisfaction, but probably the finest results were secured 

 by placing the stained plants in a 10 per cent, solution of 

 glycerin in water on a slide without a cover and permitting 

 the water to gradually evaporate until the glycerin was con- 

 centrated. Then after wiping away as much of the glycerin 

 as possible, by placing a drop of glycerin-jelly that is just 

 fluid on the specimen and covering, fine plump preparations 

 were obtained. In these the minutest details were revealed 

 without any apparent distortion. 



In studying the Cyanophycese, it has proven of great 

 value to supplement the observations made in the usual 

 manner by numerous micro-chemical investigations into 

 their composition. It is largely due to a failure to recognize 

 the micro-chemical differences in higher plants that some 

 investigators of the Cyanophycese have introduced so much 

 confusion into the cytology of these forms. 



The Cell Wall and Sheath. 



The cell wall in its younger stages gives the characteristic 

 reactions for cellulose with chlor-iodide of zinc and with 



