82 VEGETABLE SUBSTANCES. 



tion of the nitrate. The protoplasm is, therefore, 

 colored a pronounced black. (Cf. p. 41.) 



Since protoplasm is a mixture of different 

 protein compounds, it gives their characteristic 

 reaction. Living protoplasm does not, however, 

 imbibe coloring matters as dead protoplasm does. 

 A solution ' of caustic potash or concentrated 

 ammonia water increases its transparency ; acetic 

 acid produces the opposite effect. Absolute alco- 

 hol affects it very characteristically, rapidly har- 

 dening it. This is of especial value in various in- 

 vestigations of protoplasmic structure, the changes 

 which occur in the embryo sac, the division of 

 the nucleus, etc. An aqueous solution of peros- 

 mic acid, even when very dilute (i : 800), has a 

 similar effect. 



Aqueous solutions of sugar, table-salt, alcohol, 

 glycerine, etc., by the abstraction of water, cause 

 the protoplasm of cells to contract and separate 

 from the wall. This frequently happens without 

 killing the protoplasm, though this of course is not 

 the case with alcohol unless greatly diluted with 

 water. 



The metaplasm of Hanstein, 1 i. e. that part of 

 the protoplasm which holds the formative material, 

 is colored almost scarlet by Hanstein's aniline 

 violet. De Bary's epiplasm, 2 a special modifica- 



1 Organe der Harz- und Schleimabsonderung. Bot. Zeitung, 1868, 

 p. 709. 



2 Morphol. u. Phys. d. Pilze etc. Hofmeister's Handb., p. 103. 



