8o8 BOTANY AND PHARMACOGNOSY. 



Phloroglucin Solution, used as a test for lignin (p. 182), 

 is a 0.5 to 2 per cent, alcoholic solution of phloroglucin, which is 

 used in conjunction with hydrochloric acid. 



Iron Solutions are aqueous or alcoholic solutions containing 

 5 to 20 per cent, of ferric acetate or f,erric chloride. These are 

 mostly used as tests for tannin, giving either a bluish-black or 

 greenish-black coloration or precipitate. 



Copper-Acetate Solution is a 7 per cent, aqueous solution 

 of cupric acetate (p. 181). It is the most distinctive test for 

 tannin, particularly with fresh material, producing a reddish- 

 brown precipitate in the cells containing tannin. The fresh 

 material should be cut into small pieces and immediately placed 

 in the solution of copper acetate and allowed to remain for from 

 24 to 48 hours. The excess of the reagent is then washed out 

 and the material placed in alcohol. 



Schulze's Macerating Solution is prepared by adding 

 crystals of potassium chlorate from time to time to warm con- 

 centrated nitric acid. It is employed in the isolation of lignified 

 cells. The material is allowed to remain in the solution for a 

 short time or until there appears to be a disintegration of the 

 tissues. A large excess of water is then added. The material is 

 carefully washed, the cells teased apart and mounted in a solution 

 of methylene blue. 



Special Reagents comprise all those substances which are 

 employed in the morphological study of the cells, and include solu- 

 tions of the alkalies (o.i to 6 per cent.), solutions of the mineral 

 acids, which may be weak or concentrated, and solutions of 

 organic acids, as acetic and citric. 



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) 

 alcoholic solutions of haematoxylin and safranin ; (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 



i 



I 



