HOW TO KNOW THE FRESH-WATER ALGAE 



The slide should be set away under a dust-proof cover. Once or twice 

 a day for two or three days other drops of the glycerin solution are 

 added until, through evaporation of the water, approximately 100% 

 glycerin is obtained about the specimen. To this a small drop of melted 

 glycerin jelly is added and the cover slip put in place. Care should 

 be used to add just enough jelly to fill out the area under the cover 

 slip so as not to allow leakage from beneath it. The cover may then 

 be ringed with a sealing material such as balsam, colorless fingernail 

 polish, Bismark Black, or Gold Size. (See catalogues of biological 

 supply houses which list other kinds of mounting and sealing materials.) 



17 



