38o NITROGEN BASES 



substances. In the case of Cinchona, he found that the bases 

 occur in parenchyma cells, provided that they do not contain 

 calcium oxalate, either in solution in the cell sap, when the 

 tissue is very young, or in a solid state in older parts. They 

 are first formed in the leaves, and ultimately transferred to 

 the bark. 



Experience has shown that inoculation of plants with 

 pyridine or pyrrolidine derivatives produces hardly any in- 

 crease in their alkaloid content, whereas a similar inoculation 

 of dextrose or asparagine causes a considerable increase. 



On the other hand, caffeine and theobromine, which 

 strictly speaking are purines, are generally considered to be 

 decomposition products of proteins,* they are formed in places 

 of great cellular activity and their disappearance is never 

 accompanied by a concomitant increase of albuminous sub- 

 stances. 



These particular substances may correspond to urea and 

 uric acid of higher animals, for the purine nucleus is charac- 

 teristic of xanthine bases, such as uric acid ; and derivatives 

 of xanthine, such as guanine and adenine, are found in caffeine 

 and theobromine. In this connection one important point 

 of distinction between animals and plants may be mentioned ; 

 in the higher animals there is a definite elimination of these 

 waste nitrogenous substances from the organism, and the 

 output bears a definite relation to the amount of proteins 

 taken as food. In plants, on the other hand, there is no 

 general ehmination of nitrogenous waste, such substances 

 being used up in anabolic processes. Thus Weevers,t whilst 

 recognizing that caffeine and theobromine may be the pro- 

 ducts of the decomposition of proteins, considers that they are 

 reorganized, and are therefore not to be classed as waste pro- 

 ducts in the same sense as uric acid is. It will, of course, be 

 noticed that there is relatively much more- nitrogen in these 

 compounds than in the proteins. 



Finally, not infrequently is it stated that alkaloids may be 



* Clautriau : loc. cit. 



t Weevers : " Proc. Koningkl. Akad. Wetens.," Amsterdam, 1903, 

 369 ; " Ann. Jard. Bot. Buitenzorg," 1907, 21, i. 



