120 Chemistry of Mendel km Factors for Floiver-Cohmr 



of other orders (Cruciferae, Caryophyllaceae, Crassulaceae, and others) 

 only as a rule give an indirect action. It will be noted at the same 

 time that the plants whose juices give the direct action, also turn 

 brown on injury, or when exposed to chloroform vapour. Also the 

 extracts themselves, on exposure to aii-, rapidly turn brown or reddish- 

 brown. 



It is to Bach and Chodat(4) that, we owe the first suggestion that 

 ;in oxidase consists of two elements, an oxygenase which oxidises some 

 substance to the state of a peroxide and a peroxidase which then 

 transfers the oxygen of the peroxide to oxidisable substances. The 

 hypothesis has been modified both by the authors themselves and by 

 other workers : the oxygenase has been eliminated and the more simple 

 hypothesis of a peroxide-peroxidase system has been retained. 



It is now the opinion of various authors (Kastle and Loevenhart, 15 ; 

 Moore and Whitley, 20; Wheldale, 31) that those plants which give the 

 direct reaction form in their metabolism some substance which is able 

 to autoxidise and form an organic peroxide so that the system peroxide- 

 peroxidase is realisetl. 



When, in the metabolism of the plant, no substance capable of rapid 

 autoxidation is formed, the system is not able to convey the oxygen of 

 the air to the artificial acceptor, i.e. guaiacum, but can only oxidise the 

 latter when hydrogen peroxide is added. 



Hence the division of plant oxidising (nizymes into direct and 

 indirect oxidases is purely artificial. The factor of importance is the 

 peroxidase which is practically universally distributed and is the only 

 f;ictor which can be concerned in the formation of anthocyanin, for 

 anthocyanin is formed equally in jilants giving the direct or indirect 

 oxidase reaction, and moreover in a large number] of cases of plants 

 giving the direct action the albinos possess this power as well as the 

 pigmented types. 



The view that anthocyanin may be formed from a chromogen by 

 the action of an oxidising enzyme has been supported by Keeble, 

 Armstrong and Jones (14, 16, 17, IS, 19). These authors, by means 

 of an excellent micro-chemical test for oxidases, have shown that there 

 is, in many cases, an intimate connection between distribution of 

 oxidases in tissues and the distribution of anthocyanin. 



The above authors employed dilute solutions of a-naphthol and of 

 benzidine, in presence of hydrogen peroxide, as tests foi- oxidases, the 

 material used being chiefly colour varieties of fiowers and stems of 

 Primula sinenMS. 



