1922] CURRENT LITERATURE 5Or 
of flavonol-anthocyan in couples of similar glucosidal nature, but secured 
no evidence of aromatic nucleus composition in such cases. He suggests that 
these couples function as a reduction mechanism during photosynthesis. 
HELDALE® had already indicated reasons for believing anthocyan 
‘formation associated with photosynthetic defect. Noack’s work strengthens 
chloroplast integrity and anthocyan content. Especially has he shown that 
absence of carbon dioxide will cause anthocyanin formation in sunlight, and 
that engorgement with sugar probably acts indirectly (he thinks by disturbing 
the photosynthetic mechanism) in producing anthocyanins. at there are 
serious gaps in his work he has been the first to admit. He has, however, given 
with much of our knowledge. The action of narcotics, low temperatures, 
high insolation, and ultraviolet light, nitrogen and phosphorus starvation, as 
well as extremes of youth and senescence in photosynthetic organs, certainly 
fall in line with such a conception in a most disarming way. 
The formation of anthocyanins by reduction from flavonols, as well as 
WILLSTATTER’s? general scheme for color change, are elucidated by EVEREST 
and HALL” in a trenchant reply to the paper of eis SHIBATA, and 
Kastwacti." It will be recalled that the latter 1 lor conditions 
to metal organic or complex compounds of reduced flavonol glucosides, 
rather than to alkaline phenolic salts, free stages, and red oxonium salts of 
anthocyanins. In the present paper strong evidence is adduced that this 
contention is based upon work with supposedly pure substances which were 
actually mixtures, and the resultant analyses are pronounced of no value. 
It is interesting to note that Everest and Hatt now believe blue flower 
pigments to be of two general types, the alkali phenolic salt of anthocyan, 
which polymerizes to colorless on standing, and the iron double salt, stable 
in dilute solution. They have also demonstrated the existence of flavone 
but have failed to find anthocyans preceding flavone formation in flavone- 
holding organs. 
There can be little doubt that botanists are now ready to look with the 
keenest interest toward precise chemical comparisons of flavone and anthocyan 
pigments wherever the two are found associated, whether simultaneously or 
in sequence.—Pavt B. SEARS. 
8 WHELDALE, M., The anthocyan pigments of plants. 1916 (p. 81). 
9 WILLSTATTER, R., and Everest, A. E., Liebig’s Ann. Chem. 401: 189-232. 1913. 
© Everest, A. E., and Hatt, A. J., Proc. Roy Soc. B 92:150-162. 1921. 
™ SHIBATA, SHIBATA, and Kastwact, Jour. Amer. Chem. Soc. 41:208. 1919. 
