1921] CURRENT LITERATURE 333 
can be produced from flavones by reduction. In the light of this work, Miss 
‘OHLER™ was led to believe, as Nicotas and others previously ha n, 
that anthocyanin formation should be correlated with organic acid accumula- 
tion, her contention being that organic substances such as carbohydrates were 
oxidized to organic acids, thereby reducing certain flavones and causing antho- 
cyanin formation. 
he evidence for the accumulation of organic acids during formation of 
red plant pigment has been more or less contradictory. WHIESNER®™ and 
Kraus” have found that acidity of the cell sap increases during autumnal red- 
dening of leaves. Astruc’ has shown that acidity descreases in petals of 
flowers during the reddening process. The tissues immediately beneath the 
red epidermis of apples were found to be less acid than tissues beneath a green 
epidermis in the same fruit, as determined by RrvreRE and BAILHAcHE.*® 
BERTHELOT and ANDRE” state that the amount of free acid in the plant as 
determined by titration of expressed juice bears no relation to the total amount 
of organic acid in the plant, as for the most part the acids are combined as 
salts of plant bases. Miss Kouter also objects to titration of expressed juice 
because of the tendency of the alkali used to combine with phenolic compounds 
such as tannins and anthocyanins. After several unsatisfactory attempts to 
precipitate the phenolic compounds by the use of hide powder, zinc acetate, and 
analgesine (antipyrine), Miss Kouter found that free organic acids could be 
quantitatively dialyzed out of the expressed juice and therefore used this 
ethod in her work. The acids were then titrated with a base and calculated 
as free organic acid. Combined organic acids were determined, using oven 
dried samples of tissue, by heating at dull red heat in a muffle. A known 
quantity of N/r1o sulphuric acid was then added to the ash to neutralize the 
bases liberated by the combustion, and the acid residue titrated with alkali to 
d how much acid was neutralized by the ash. € e obtained in this 
way was added to that of the free organic acid and the sum placed under the 
caption “total organic acids.” Total organic acids determined in this way 
were found to increase in corollas of Cobaea scandens during the process of 
development from bud to mature flower, along with anthocyanin development, 
” KonLer, DENISE, Etude de la variation des acides organiques an cours de la 
pigmentations anthocyanique. Memoir to Faculty of Science, Univ. Paris. 1921. 
SNER, J., Untersuchungen iiber die Herbstliche Entlaugung der Holzge- 
wachse. "Sis. Ber. Akad. Wiss. 64:465-510. 1871. 
™ Kraus, C., Studien iiber die Herbstfarbung der Blatter und iiber Bildungweise 
der Pflanzensauren. Buchner’s Repert. Pharm. 22: 273. 1873. 
*s Astruc, A., Recherches sur l’acidity végétale. Ann. Sci. Nat. Bot. 17:65-109. 
Tg03. 
© Riviere, G., and BarHacue, G., De Vinfluence de la lumiere directe sur la 
composition pie des fruits. Jour. ‘Soe. Nat. Hort. France, IV. 9:627. 1908. 
7 BERTHE M., and AnpbrgE, G., hate sur la gaat des acides chez 
les vegetaux. Compt. Rend. Acad. Sci. 327502. 
