Cytology and Movements of the Cyanophycee. 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 Io 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 Cyanophycee, 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 Cyanophycez 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 
