860 Wisconsin Academy of Sciences, Arts, and Letters, 
pigments in some plants, while not satisfactory in every detail, 
is a long step in advance. This work not only explains much 
concerning the chemistry of the anthoeyanin pigments that has 
hitherto been unexplained; but it places the anthocyanins in 
a class, and shows the close chemical relationship between the 
various anthoeyanin pigments studied, and also between the 
anthocyanins and other pigments occurring with them in the 
plant. 
Anthocyanins are the red, blue and purple pigments extracted 
from flowers, fruits, and leaves by water and dilute alcohol. 
They are insoluble in ether, are turned red by acids, blue or 
green by alkalies, and give green, green-blue, gray-green, or yellow 
precipitates with lead acetate. It is commonly supposed that 
the purple color of flowers and fruits is due to the free pigment, 
the blue color to an alkaline combination, and the red color to 
an acid combination of the pigment. 
The anthocyanins, according to Willstaetter, are present in 
the plants only as glucosides, sometimes as mono- and some¬ 
times as diglucosides. The sugar molecule with which the pig¬ 
ment is combined is generally that of glucose, though in at 
least one instance galactose is present. The anthocyanins all 
exhibit a characteristic reaction, the anthocyanidin reaction. 
An anthoeyanin dissolved in a normal or twice normal solu¬ 
tion of sulphuric acid is unaffected by shaking with amyl alco¬ 
hol. After hydrolysis, however, the colored anthocyanidin is 
quantitatively extracted by the amyl alcohol, forming a reddish 
violet solution which slowly, more rapidly in the presence of 
sodium acetate, changes to a bluish violet. 
All of the anthocyanins so far studied are very closely related, 
the color bases of the various glucosides being hydroxy and 
methoxy derivatives of pelargonidin, the least highly oxygen¬ 
ated of the known anthocyanins. They are also closely re¬ 
lated to the flavone derivatives, so many of which constitute 
the yellow plant pigments, and many of which occur-side by 
side with the anthoeyanin pigments in the plants. Accord¬ 
ing to Willstaetter the free anthoeyanin pigments are isomers 
of some of the flavone pigments, the isomerism between them ex¬ 
isting, not in the position of substitution in one or the other of 
the two benzene nuclei, but in the transformation, by the chang¬ 
ing of valence of the ether oxygen from' two to four, of the 
pyron to a pyrylium grouping, and of a difference in the posi- 
