154 THE CHEMISTRY OF THE PLANT 



Formaldehyde Con. hydrates. Found free in 



minute quantities in leaves 

 when active photosynthesis is 

 occurring. 



Asparagin This is found, especially in the 



C4H 8 N 2 03, (CO(NH 2 ) CH 2 growing regions, in many 



- CH(NH 2 )-COOH). plants, e.g. asparagus, peas, 



beans, vetches, beet roots, 



potatoes, etc. 



Chitin This forms part of, or in some 



CigH3oN 2 Oi2 cases is the chief constituent of, 



the cell wall of many of the 

 lower plants, e.g. Myxo- 

 phyceae, Mucorales, Carpo- 

 myceteae. It was long con- 

 sidered a form of cellulose 

 ("fungus cellulose"). It 

 forms the body wall of insects, 

 crustaceans, etc. 



Vanillin Formed by the fermentation 



of the seed pods ("beans") of 

 the Vanilla plant, whence it is 

 extracted by alcohol. It is 

 present in most if not all 

 lignified cell walls and is 

 possibly one of the substances 

 giving the cell wall the char- 

 acters that we call "lignifica- 

 tion" (see hadromal). 



Hadromal (composition uncer- This is a substance separated 

 tain) by Czapek from lignified cell 



walls and believed by him to 

 be what gives them their 

 "lignified" character. On the 

 other hand many botanists do 

 not consider this as the impor- 

 tant body and ascribe lignifica- 

 tion to the presence in the cell 

 walls of coniferin and vanillin 

 (q.v.) and perhaps other sub- 



