BOTANICAL MICROTECHNIQUE. 



gradually allow water to enter from the edge of the cover- 

 glass. 



The dissimilar behavior of the gums with iodine solutions 

 and with cuprammonia has already been mentioned. Be- 

 sides these, corallin may be used in many cases in the study 

 of gelatinized cell-walls and gums, since many of them are 

 deeply stained by it. Since it is practically insoluble in 

 water, it may be dissolved in a concentrated solution of 

 soda. This solution gradually decomposes, but preserves 

 its staining power for a long time (cf. also 289). 



Characteristic stainings of plant-mucilages are often ob- 

 tained with Hanstein's aniline mixture.* 



a. Amyloid. 



276. The substance known by the name amyloid occurs 

 in the seeds of various plants (Tropceolum ma/us, Impatiens 

 Balsamina, Pczonia officinalis, many Primulacece, and others) 

 and constitutes a reserve material which goes into solution 

 on the germination of the seed. 



Amyloid is characterized by being colored blue by iodine 

 solutions, the best adapted for this reaction being, according 

 to Nadelmann (I, 616), a dilute solution of iodine and 

 potassium iodide, since a concentrated solution of the same 

 substances colors it brownish orange, and fresh tincture of 

 iodine does not generally color it at all at first. 



In cuprammonia amyloid is insoluble. 



Its behavior with nitric acid is also characteristic. 



In an acid which contains 30^ of HNO 3 (spec, gravity 

 1.285), amyloid at once swells strongly, and after a time 

 .becomes entirely dissolved (cf. Reiss I, 735, 737, 739). 



The amyloid contained in the seeds named is not identical 

 with the compound prepared from cellulose by treatment 

 with acids ( 246), which has often been termed amyloid 

 (cL Beilstein I, 863, 882). Amyloid is distinguished from 

 reserve-cellulose (cf. 286) by the reactions already de- 



* [This consists of an alcoholic solution of equal parts of fuchsin and 

 methyl violetj 



