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A TEXT-BOOK OF BOTANY. 



DOUBLE STAINING, or the use of two stains in the examination 

 of a specimen, furnishes not only a means of beautifying the speci- 

 men, but also has a certain diagnostic value. The following are 

 some of the combinations used: (a) aqueous solutions of car- 

 mine in connection with alcoholic solutions of iodine green; (b) 



FlG. 419. Crystals of some of the common reagents which not infrequently sepa- 

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

 which occur in cubes about 10 M in diameter or long needles about 50 ^ long; B, phloro- 

 glucin which occurs in broad rectangular plates or ellipsoidal discs from 10 to 35 M- in diam- 

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

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

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



alcoholic solutions of haematoxylin and saf ranin ; (c) solutions of 

 eosin and methylene blue; (d ) solutions of fuchsin and methylene 

 blue; (e) solutions of gentian violet and Bismarck brown. 



MOUNTING OF SPECIMENS. Microscopic preparations or 

 mounts are of two kinds : they may serve a temporary purpose 



