139 
tie of a greenish hue, or are entirely white. These 
white leaves, however, have been shewn (373.) to 
contain the same colourable juices as those which 
are green, and, when extracted by alkohol, they pass 
to a green colour by the addition of alkaline matter. 
Hence the colourable matter is more or less distri- 
buted through the whole plant ; and, in the manner 
already stated, it is rendered white or green accord- 
ing as the plant, or any part of it, is exposed to, or 
secluded from light. This colourable matter, as we 
before remarked, is chiefly contained in the paren^ 
chyme of the leaf, and the colour is transmitted 
through the epidermis which invests it. 
393. In the red variety, however, the colour is 
not communicated by the juices of the parenchyme, 
but by the outer skin or- epidermis itself ; while the 
parenchymatous juice beneath is yellow or white. 
The redness, too, of this plant is seen both in those 
leaves which are secluded from light, and in those 
which are exposed to its action ; consequently this 
agent exerts no immediate effect in their colouration. 
The leaves of this cabbage yield a bluish tint to wa- 
ter, which, like that of turnsole, is rendered red by 
exposure to the air, or by impregnating it with car- 
bonic acid. In the same manner, it is rendered green 
by alkalis, so that the red cabbage must contain a 
colourable matter, similar to that which is diffused 
through the green and white leaves of the common 
variety. This, indeed, is easily seen by inspecting 
the plant itself ; for though the skin of its leaves is. 
red, yet the parenchyme of the outer leaves is, in 
many parts, sensibly green, and transmits even a 
