135 
which passes afterwards to orange. If sulphuric a-- 
cid be poured into the green solution, it reddens it ; 
and the red tincture is rendered green by alkalis. 
The red leaves of this vine lose their colour in wa- 
ter charged with sulphuric acid, but the water ac- 
quires a lively red tinge ; and the same leaves, im- 
mersed in an alkaline solution, have resumed almost 
their primitive green colour *. As thus the leaves 
of the same plant, in their green and red states, 
yield their respective colours to alcohol ; as these dif- 
ferently coloured solutions pass to red or green, ac- 
cording as acid or alkaline matter is made to predo- 
minate in them ; and as the entire leaves themselves 
exhibit similar variations in colour, when exposed to 
the operation of the same agents, we may fairly con- 
clude, that the several tints which these leaves exhi- 
bit, in the successive periods of their growth, matu- 
rity, and decay, depend essentially on analogous 
changes, which take place in the condition of their co- 
lourable juices, according as these juices are modified 
by the operation of those causes, which vary the state 
and proportions of their acid and alkaline matter. 
388. This redness of autumnal leaves, M. Geof- 
froy, indeed, ascribed to an acid developed at that pe- 
riod, which, by overpowering the alkali, gave rise to 
the red colour, in the same manner as distilled vinegar 
changes a green solution to a red colour f- And M. 
Senebier himself, who, as we have seen, attributes the 
Mem. Phys. Chim. t. iii. p 77- et seq, 
Mem. de TAcad, an. 1707- 
