INDICAN 189 



genin, sa*ligenase produces catechol from the saligenin, and 

 when the leaves decay a third enzyme, catecholase, produces 

 from the catechol an amorphous black pigment. He found 

 that in places where depletion of salicin was taking place 

 the saligenin appeared in quantities insufficient in amount to 

 account for the whole of the salicin ; also that catechol oc- 

 curred in such places, after the glucoside had disappeared, in 

 a sufficiently large quantity to warrant the above conclusion. 

 Weevers considers that when glucose and catechol are pro- 

 duced the sugar is translocated, whilst the catechol remains 

 in situ, and combines with fresh glucose, and so reconstructs 

 salicin. 



INDICAN. 



Indican,* C 7 H 6 NC. O . C 6 HnO 5 , is the name given to a 

 glucoside which occurs not only in Indigofera anil, I. arrecta, 

 I. tinctoria, and /. sumatrana, but also in other plants, such as 

 Isatis tinctoria, Polygonum tinctorium, species of Phajus and 

 other orchids, e.g. Calanthe and Strobilanthes. In the plant, 

 indicane is well distributed in the aerial organs. Thus in Indi- 

 gofera, it is found in all the tissues of the leaf except the 

 tracheae of the xylem, it is also abundant in the apex of the 

 stem in all tissues except the wood vessels and the laticiferous 

 system. The flowers also have a small quantity, but the root 

 is characterized by its absence, f 



At one time it was considered that the chloroplasts played 

 an important direct part in the formation of indicane, but Leake 

 can find no evidence of this. 



Identification. 

 I. The tissue may be boiled in a 2 per cent solution of 



* The name indican is also applied to a compound of the formula 



C O . SO 3 K 



/\ 



C 6 H 4 CH 



V \ 



This substance, which is more correctly described as indoxyl potassium sulphate, 

 occurs in small quantities in human urine and also in the urine of herbivora. 

 t Leake: " Ann. Bot.," 1905, 19, 297. 





