COLORING MATTERS OF LEAVES AND FRUITS. 
31 
from its solution in potassa by the acids, in pale yellow 
flocculi, which, when properly washed, do not redden litmus 
paper. It is but little, if at all, soluble in carbonate of potassa, 
and insoluble in caustic ammonia, to which, however, it com- 
municates a yellow color. 
This coloring matter is then a peculiar fatty matter, inter- 
mediate between the fatty oils and the resins, which may be 
whitened without loosing its properties, of difficult solubility 
in alcohol, and of being fatty and oily. We may name it 
zanthophylle (from tavflo? yellow, and $v%%ov a leaf.) We 
have every reason to presume that in the disappearance of the 
green color and its change into yellow, this is produced from 
the green by means of a change of organization of the leaf, 
effected by the cold, and which modifies the organic opera- 
tions. But it was in vain that I endeavored to reproduce the 
green color by means of the yellow; besides, I could not suc- 
ceed in changing the green to yellow. The brown color of 
the foliage has nothing in common with the yellow. It is 
produced by an extractive principle, before colorless, which, 
after the disorganization of the epidermis of the leaf, becomes 
brown by the action of the oxygen of the air; it then com- 
municates to the fibres of the skeleton of the leaves a brown color 
which cannot be taken away even by digestion in a weak solu- 
tion of caustic potassa, or which the long continued action of 
sulphuretted hydrogen cannot destroy. 
2. Bed coloring matter of fruits. 
The red color of many species of fruits has, in general, been 
considered as a blue color reddened by an acid; this may be the 
case in many instances, but it is not so in all; and consequently,, 
the coloring matter of those which are exceptions should be 
separately determined. I have examined the color of the 
cherry, (Prunus cerasus,) and of the currant, {Ribes nig- 
rum;) both contain the same coloring matter, and this is not 
a blue. The presumption that it was this latter color may 
have arisen from the fact that the juice of these fruits gives a 
blue precipitate with acetate of lead; but these precipitates 
are the malate and citrate of lead, with which the coloring mat- 
