POTASSIC HYDRATE. 13 



Cell-walls (wood-cells, ducts, etc.), that do not 

 immediately give the cellulose reaction with iodine 

 and sulphuric acid, because of the presence of 

 so-called incrustation matters, give this reaction 

 promptly after treatment with boiling potash 1 

 often used in connection with nitric or other 

 acids since this removes the foreign sub- 

 stances. 



Sometimes tannin may be recognized by the 

 use of potash, as cells which contain it and 

 which color green with salts of iron assume a 

 yellow color with potash. 



Cells containing chrysophanic acid 2 become pur- 

 ple-red with the same fluid. 



Sachs has employed potash as an analytic re- 

 agent in various histologo-physiological studies, 

 obtaining good reactions when using it with cupric 

 sulphate in testing for different sugars, protein 

 matters, and carbo-hydrates. 3 



When protoplasm is first treated with nitric acid, 

 and afterwards with dilute potash or ammonia, it 

 assumes a beautiful yellow color from the forma- 

 tion of potassic or ammonic xanthoproteate. 4 



The so-called crystalloids swell and change their 

 angles in potash, thus showing their organic 

 nature. 



1 Hofmeister : Handbuch, I., several places. 



2 Borscow : Bot. Zeit, 1874, p. 20. Weiss : Allg. Bot., 1878, I., p. 288. 

 * See cupric sulphate, below. The reader is referred to the preceding 



papers, and to H. de Vries' Keimung des rothen Klees. Landwirthsch. 

 Jahrb., 1877, VI., p. 468. 



4 Dippel : Das Mikroskop, II., pp. 10, 18. 



