78 VEGETABLE SUBSTANCES. 



difficulty in concentrated chromic acid ; soluble in 

 the Schultze maceration fluid (which is specially 

 important in the investigation of wood), and occa- 

 sionally in hot potash, sometimes even in boiling 

 water. 



The intercellular substance is easily and strongly 

 colored by- the aniline dyes. With chlor-iodide of 

 zinc it assumes a yellow color. Hot nitric acid 

 and ammonia give it a beautiful yellow color. 1 



SUBERIN, 



The constituent of cork, is insoluble in concentrated 

 sulphuric acid and cuprammonia, and very resistant 

 to chromic acid. Treated with boiling potash, 

 corky membranes secrete peculiar ochre-yellow 

 granular masses, and when heated with nitre acid 

 and chlorate of potassium they form masses of 

 eerie acid, which are soluble in alcohol, ether, 

 benzole and chloroform. 



The walls of cork cells are colored yellow by 

 chlor-iodide of zinc. Grenacher's alum carmine 

 does not stain them. 



Olivier indicates the following method of color- 

 ing corky membranes. Sections of the tissue to 

 be studied are laid in a solution of fuchsin in 

 equal parts of alcohol and water, which is taken 



1 Solla: Beitr. zur Kenntniss d. chem. und phys. Beschaffenheit der 

 Intercellularsubstanz. Oesterr. botan. Zeitschr., Nov. 1879. Hohnel : Mit- 

 tellamellc der Holzelemente u. d. Hoftiipfelschliessmembran. Bot. Zeitung, 

 1880, No. 26. 



