QO VEGETABLE SUBSTANCES. 



assume with iodine, and the blue or violet brown 

 imparted by iodine and sulphuric acid. Many 

 of them swell considerably in water. Barcianu 1 

 gives the red color induced in tissues which 

 contain mucus, by successive treatment with 

 creosote, chloride of tin and aniline (?), as a re- 

 action. 



The so-called amyloid (Schleiden, 1844) must 

 belong here. 2 Leguminous amyloid is colored blue 

 by iodine in alcohol, and yellow by iodine in water. 

 It is soluble in dilute alkalies and in boiling water. 



Hanstein's aniline violet colors amyloid sub- 

 stances red, but of a shade different from that 

 obtained in the gum and tannin reactions. 3 



TANNIN (Tannic Acid). 



Cells containing this substance are colored deep 

 blue or green by treatment with ferric acetate (p. 

 42) or chloride (p. 33). They are colored reddish 

 brown by bichromate of potassium (p. 40), fulvous 

 by Hanstein's aniline violet (p. 60), and red or 

 violet by dilute chlor-iodide of zinc (p. 9). All of 

 these reactions demand a prolonged stay in the 



1 BlUthenentwickelung der Onagraceen. Schenk and Luerssen's 

 Mittheil. aus der Bot., II., Heft i, p. 85. I have not made myself familiar 

 with this reaction. 



2 Vogel and Schleiden: Amyloid. Schleiden's Beitr. z. Bot., 1844, 

 Bd. I., VIII. 



3 Cf., further, Leon-Marchand : G61atine produite par les Algues. 

 Bulletin de la Soc. bot. de France, 1879, P- 3$7- 



