POTASSIC HYDRATE. 9 



converts this substance into amyloid, which is 

 then colored blue or violet by the free iodine. 

 Cell-walls that have suffered degeneration of the 

 cellulose are not colored blue. Wood-cells, ves- 

 sels, cork-cells, and the cells of the root-cap, as 

 well as the cuticularized layer of the epidermis, 

 the extine of pollen grains and spores, in fine, all 

 lignified or corky membranes, are colored yellow ; 

 the true cuticle, however, is uncolored. Starch 

 colors blue, but the grains rapidly swell up and 

 undergo disorganization. The walls of fungus 

 hyphae, composed of the so-called fungus-cellulose, 

 remain uncolored to a noticeable degree. 1 [They 

 are also usually uncolored by sulphuric acid and 

 iodine.] 



For the detection of tannin, a very dilute solution 

 of chlor-iodide of zinc is employed, the contents 

 of cells which contain tannin becoming reddish or 

 violet under this treatment. 2 



POTASSIC HYDRATE (Caustic Potash). 



Next to iodine, caustic potash takes the most 

 important place among micro-chemical reagents. 3 



1 Schacht: Die Pflanzenzelle, p. \\$,et seq. Hofmeister: Handbuch, 

 I., Die Pflanzenzelle, p. 258. 



2 Sanio: Bot. Zeit, 1863. Dippel. Das Mikroskop, I., p. 375. 



8 Nageli: Das Mikroskop, 1877, pp. 472 and 525. Dippel: Das Mik- 

 roskop, I., p. 278. Wiesner: Technische Mikroskopie, 1867. Sachs: 

 Ueber die StofT-, welche das Material der Zellhaute liefern. Jahrb. fiir. 

 wiss. Bot., 1863, III.; Keimung von Allium Cepa. Bot. Zeitung, 1863, 

 Nos. 8-9 ; Zur Keimungsgeschichte der Graser, Keimung der Dattel. 

 Bot. Zeitung, 1862. 



