POTASSIC HYDRATE. II 



[A slight coating of paraffine will prevent the 

 stopper from sticking.] 



In microscopic manipulations the value of potash 

 depends upon its solvent and softening actions, 

 those which accompany the absorption of water. 

 It dissolves many of the fine granules in proto- 

 plasm, bleaches various coloring matters, forms 

 soluble soaps with fats, and effects the swelling of 

 the starch which often renders tissues opaque. It 

 thus destroys the protoplasmic structure of cells 

 and makes these clearer and more transparent, 

 thus, when dilute, playing a very important part 

 as a clearing medium in the study of otherwise 

 opaque sections ; while it permits the examination 

 of thick masses of tissue, or even of entire organs, 

 as embryos, trichomes, sections of the punctnm 

 vegetationis, or whole stems and leaves, as in the 

 study of the course of fibre-vascular bundles [and 

 laticiferous tissue]. 1 



This method was first proposed by Hanstein. 

 The sections are treated with a solution of potash, 

 washed, and neutralized with hydrochloric or acetic 

 acid. If this renders them too opaque they may be 

 cleared by washing first in pure water, then in 

 ammonia water. If, on the other hand, they are 

 too transparent, they may be improved by washing 



1 Hanstein : Die Scheitelzellgruppe im Vegetationspunkt der Phanero- 

 gamen, 1868; Entwickelung des Kcimes, Botan. Abhandl., I., Heft i, p. 5. 

 Koch: Cuscuta, in Hanstein's Bot. Abhandl., II., Heft 3, p. 25. Oels : 

 Anat. d. Droseraceen., Diss., Breslau, 1879, p. 13. 



