A GENETTCO-rHYSIOLOGICAL STUDY ON THE FORMATION ETC. 
25 
that there may "be no appreciable amount of the chromogenic substance ac¬ 
cumulated to show a definite colour reaction. 
The body of evidence so far reported seems to point to the following 
conclusions. 
In a number of plants, anthocyanin and the brown pigment (phloba- 
pliene) can be traced to their respective chromogenic substance previous to 
the formation of the pigments. Both pigments can be formed from the same 
chromogenic substance by the action of a number of complementary pigment- 
yielding agencies. The chromogenic substances can be identified as belonging 
to two groups of substance with respect to certain colour reactions, one of 
which is designated as chromogenic substance F, (certain flavones and 
flavonols), and the other as chromogenic substance P of which the chemical 
nature is unknown. 
The formation of brown pigment includes at least the following cases. 
1. It is chiefly due to the oxidation and subsequent changes of the 
chromsgenic substance F. Example : the awn of Oryza saliva as w T e shall see 
later. 
2. It is chiefly due to the oxidation and subsequent changes of the 
chromogenic substance P. Example : the seed coat of the legumes ( Phaseolus 
vulgaris, Pimm sativum, Glycine soja etc). 
3. It is cheifly due to the oxidation and subsequent changes of the 
chromogenic substance F and P. Example : the barks of many trees ( Cry- 
ptomeria japonica, Pinus parvifolia, Platanus occidentalis etc). 
Besides those chromogens, tannoids, and carotinoids may play a role in 
the production of the reddish and yellowish brown pigments. 
% 
Table 13. 
Showing the chromogen content of the plant extracts. 
Designations : Peri. = peripheral tissue. 
Int. = Internal tissue. 
( + ) sign without the number of the class in the colour scale, 
denotes the presence of the colour but below the lowest class in the scale. ( + ) sign with the 
numeral denotes the colour somewhat deeper than the scale indicated by the numeral. ( —) sign 
designates likewise the colour below the scale. 
