COLORING MATTERS OF LEAVES AND FRUITS. 
29 
color of the petals of flowers. These results are by no 
means exact; the yellow foliage does not become again green 
by the action of any reagent; but the leaves having become 
red, recover their green color by means of potassa, because 
the red coloring matter forms green combinations with that 
alkali. Leopold Gmelin first directed attention to the inexacti- 
tude of the results of Macaire Prinsep. Inspired by this ob- 
servation, I engaged in some researches upon the color of fo- 
liage altered by the influence of the cold of autumn. I have 
experimented especially upon the citron-yellow foliage of the 
Pyrus communis, which was placed, while yet fresh and 
immediately upon being gathered, in a flask, and completely 
covered with alcohol of 0.833, in contact with which it was left 
for forty-eight hours. The alcohol became of a yellow color, 
but the foliage still remained yellow, but paler than before; 
the alcohol was decanted, and the flask placed in an inverted 
position for some time; the foliage then became of a brown 
color throughout, wherever it was touched by the air, but in 
those parts in contact with the sides of the vessel the yellow 
color was preserved. Alcohol was poured upon the leaves 
several times, and each time it became of a yellow color; 
finally, the alcohol was boiled; it again took a yellow tinge, 
but became gelatinous on cooling. 
The macerating liquors were distilled to one-eighth; there 
was then deposited, upon cooling, a granulent matter, which 
presented some appearance of crystallization. After the se- 
paration of this substance, the distillation was continued, until 
there remained nothing but the water of vegetation of the 
leaves. On the top of this yellow liquid, there floated a yel- 
low, soft, fatty substance, which appeared to be identical 
with the granules which contained the coloring matter of the 
foliage. These granules did not exhibit, under the microscope, 
any indications of crystallization, but could be spread out by 
the fingers into a greasy yellow spot; it was mixed with a fatty 
oil, which I could distinguish, butcould not separate completely, 
and another substance likewise fatty. It could be partly 
purified from the former, by digestion with a weak solution 
