A GENETICO-PHYSIOLOGIC AL STUDY ON THE FORMATION ETC. 
23 
Tlie skin of the young, green grapes was found to be very rich in the 
chromogenic substance P but it contains only a trace of the cliromogenic 
substance F. It is of interest to find that the “ white ” varieties, so far 
examined, contained the chromogenic substance as much as that shown by 
the coloured varieties. Even in the deep black variety, the reduction colour 
of the extract of the green skin was only faint, so it seems highly probable 
that the antliocyanin pigment in the skin of the grape may be formed chiefly 
from the chromogenic substance P rather than the chromogenic substance F. 
According to Willstätter and Zollinger (1915) 1 the antliocyanin of grape 
skin (North Italian or hothouse) were ænidin and ænin which are the methyl 
ethers of delphinidin and delphinin respectively. The chemical investigation 
of the chromogenic substances in the grape skin is inviting, for it may clear 
the relation of antliocyanin to the chromogenic substances P and F. 
Dezani found two kinds of the chromogenic substances in the white grapes 
of which one only is precipitated by lead acetate. By the action of hydro¬ 
chloric acid, colouring matters are obtained which are analogous to the ænocy- 
anins. The conversion of these substances into colouring matter is due not 
to oxidation, but probably to hydrolytic scission with simultanious formation 
of a reducing substance. In the residue from the chromogenic substances there 
are other substances which give a red colour with alkali. The result obtained 
by Hedrick and Anthony 2 shows that (1) “white” is a pure, colour, namely 
“white” x “white” gives only “white”: and (2) “white” is recessive to 
both black and red. 
Table 12. 
Cliromogen content of tlie skin of green grapes. 
Name of variety 
Colour of skin when 
fully ripe 
Chromogen P. 
Cliromogen F. 
“ Ives Seedling ” 
Black 
I 
VI 
“ Bacon ” 
» 
yy 
I 
VI 
1. "Willst atter, It. and Zollinger, E. H., Ueber die Farbstoffe der Weintraube u. der 
Heiderbeere. Liebig. 408:83, 1915, and 412:195, 1916. See also Dezani, S., loc. cit. 
2. Hedrick, U. P. and Anthony, R. D., Inheritance of Certain Characters of Grapes. N. 1. 
Agric. Exp. Station. Technical Bull. 45. 1915, pp. 19. 
