A GENETICO-PH Y SIOLOGIC AL STUDY ON THE FORMATION ETC. 
13 
a, group of substances such as maclurin, luteolin, catechiu, quercetin and 
scoparin, also fields protocatechuic acid and phloroglucin as their decomposi¬ 
tion products. So he supposed that those phlobaphenes which yield protocate¬ 
chuic acid and pliloroglucin are the derivatives of the substance just mentioned. 
In the epidermis of leaves and the periphery of the bark, those substances may 
undergo oxidation by the contact with air resulting in the formation of 
phlobapliene. 
Walter (1890) 1 studied the sklerotic tissue of tlie rhizome of ferns and 
came to the conclusion that the brown pigment deposited in the membrane 
is identical with plilobaphene and its physiological function was considered by 
Trim to be the protection of the tissue from the injurious effect of the humidity 
of the substrate under which these plants grow. 
Some of the brown pigments found in nature are hardly soluble in common 
organic solvents like ether, alcohol, benzine, and acetic ether, but are readily 
soluble in water and especially in alkaline solutions, yielding a deep brownish 
red to wine red colour, which by acid is instantly changed to yellow. The 
brown and reddish brown oxidation products of flavones and flavonols as already 
stated in the preceding chapter, possess similar properties. Since the flavone 
derivatives are widely distributed in plants, it seems quite probable to assume 
that some of them give rise to plilobaphene by oxidation as Hlasiwetz has 
already supposed. Therefore, w r e may regard certain flavone and flavonol 
derivatives as the chromogen of both antliocyanin and plilobaphene pigments. 
We assume that certain relations existing among these pigments may be 
somewhat as follows : 
Chromogenic 
substance 
Initial change 
Subsequent 
changes 
Product 
Certain flavones 
reduction 
formation of com- 
anthocyanins of 
flavonols and their 
plex with salts 2 
different hues. 
glucosides 
oxidation 
condensation & 
polymerization 
plilobaplienes 
1. "Wärter, G., lieber die braumvandigen sklerotischen Gewebeelemente der Farne, mit 
besonderer Berücksichtigung der sog. “ Stützbündel ” Eussow’s. Bibliotheca Botanica. Heft 
18 : 21, 1890. 
2. See Shibata, K, Shibata, Y. and Kashiwagi, I., Studies on Anthocyanins. Color Varia¬ 
tion in Anthocyanins. Jour, Amer. Chem. Soc. 41:208, 1919. 
