8io 



BOTANY AND PHARMACOGNOSY. 



examined again. After this preliminary examination other agents 

 and reagents may be employed. Specimens mounted in glycerin 

 will keep for several days and even months. Generally speakmg, 

 the only effect which the glycerin has on the tissues or contents 



Fig. 327. Crystals of some of the common reagents which not mfrequently sepa- 

 rate on the slide and may be mistaken for cell contents: A, isotropic crystals ot chloral 

 which occur in cubes about 10 fi in diameter or long needles about 50 n long; a. pnioro- 

 glucin which occurs in broad rectangular plates or ellipsoidal discs from 10 to 35 ^^ in ai^m- 

 eter which are doubly lefracting with a play of colors; C, cubes of potassium iodide whicn 

 are isotropic; D, crystals from potassium hydrate solution which separate in broad pnsms 

 and branching chains that are doubly refracting and give marked color effects. 



is that of swelling them, which is obviated, to a greater or less 

 extent, however, if the glycerin is washed out after an exam- 

 ination is made. 



In addition to the methods involving the use of glycerin, there 

 are two ways of making permanent mounts, depending upon the 

 employment either of Canada balsam or glycerin jelly as the 



