136 
green colour to a cause different from that of an al- 
kali, nevertheless ascribes the red colour, in these 
instances, to the predominance of acid matter, which 
is developed under that incipient decomposition 
which the leaves, at the decline of vegetation, expe- 
rience *. The production of acid matter by vege- 
table infusions, in their transition from a green to a 
red colour (372.), leads M. Berthollet also to believe, 
that an acid may be developed in those leaves which, 
in autumn, redden before they pass to yellow t 
389. But besides this red colour, which the leaves 
of different plants exhibit, in the more advanced pe- 
riods of their vegetation, there are other leaves, says 
M, Senebier, which proceed red from their buds, 
and become green only in the latter periods of their 
growth ; such are those of the apricot, the walnut, 
the maple, and the pear, the leaves of which last plant 
are of the same colour in their earliest and most ad- 
* ' : 
vanced age J. In these instances, in which the young 
leaves are at first red, it is easy to suppose, that the 
colourable juices contain an excess of acid, which en- 
ables them to exhibit this colour ; but by the action 
of the solar rays, this excess, at a later period, is 
reduced, and the alkali becoming finally predomi- 
nant, gives rise to its accustomed hue. In the young 
leaves of most buds, the colour is only white, indi- 
cating a less proportion of acid ; and these leaves, 
* Mem. Phys. Chim. vol. iii. p. 83. 85. 
f Elemens de la Teinture, vol. i. p. 57 . 
j Mem. Phys. Chim. t. iii. p. 7o. 
