A GENETICO-rHYSIOLOGIC.\L STl'DY UN THE FOIOrATION ETC. 25 



tliat there may Ije no appreoiiiblo lunoiint of tlie cLromogcuic substance ae- 

 cnijiidated to sliow a ilefiiiite colour reactiou. 



Tlie body of evidence so far rejxirted seeius to point to tlie following 

 conclusions. 



In a number of plants, autbocyaniu and tlie br(jwu pigment (pbloba- 

 phene) vnn 1)6 traced t.) their rospactive chi-omogenic substiince pre^•ious to 

 the formation of the pigments. Both pigments can be formed fi-om the same 

 cliromogenic substance by the action of a number of complementary pigment- 

 j-ielding agencies. The clu-omogeuic substances can te identified as belonging 

 to two giHJups of substance with respect to certain colom* reactions, one of 

 which is designated as chromogenic substance F, (certain flavones and 

 flavonols), and the other as clii-omogenic substance P of which the chemical 

 natiu« is luikuown. 



The formation of brown pigment includes at least the following cases. 



1. It is cliiefly due to the oxidation and subsequent changes of the 

 chromsgenic substance F. Example : the awn of Onjza scdiva as we shall see 

 Liter. 



2. It is diiefly due to the oxidation and subsequent changes of the 

 chixjmogeuic substance P. Example : the seed coat of the legumes {Pkiseolus 

 vulgaris, Pisum sativum. Glycine sqja etc}. 



3. It is cheifly due to tha oxidation and subsequent changes of the 

 chromogenic substance F and P. Example : the barks of many trees ( Cnj- 

 ptomcria japonica, Pimts parvi/dia, Plcdanus occidentalis etc). 



Besides those chromogens, tannoids, and Carotinoids may play a role in 

 the pi-oduction of the reddish and yellowish lirowu pigments. 



T.iliLE 1.3. 



Showing the chroinogen content of the i^lant extracts. 

 Designations : Peri. = iieriphernl tissue. 

 Int. = Interna! tissue. 



( + ') sign w-ithout the number of the class in the colour scnie, 

 denotes the presence of the colour but below the lowest class in the scale. ( + ) sign with the 

 nnmemi denotes the colotir somewhat deeper than the senle indicated by the numeral. ( — ) sign 

 designates hkewise the colour below the scale. 



