21 
whether it is true or not. But the proposition must 
be received with considerable limitation if we look to 
plants. Colour very often has, in plants, an unrnis- 
takeable connection with form. In fact, the nature 
of plants renders it inevitable. Colour in plants,— 
especially the variegations of colour, mottlings, mark¬ 
ings, and blotches, are generally produced by the 
action of some substance introduced into the system 
of an organ by its veins. The veins are symme¬ 
trical, and the matter introduced through them, acting 
in the vicinity of the veins, discharges colour. The 
colour therefore has some relation to the veins, and 
therefore must be symmetrical. 
44. Of this truth endless examples meet us at every 
step. Any one may procure a piece of the variegated 
Aloe leaf, in which veins run parallel to each other, 
from the base to the apex. These veins, towards 
the margin, appear to have the power of discharging 
the green colour, and thus the variegation of the Aloe 
runs in streaks following its symmetrical veins. 
45. In the reticulated Amaryllis the leaf is always 
white in the centre ; the matter which has the pro¬ 
perty of discharging colour is confined to the middle 
mid-rib, and cannot get beyond it. 
46. But wc need not visit hot-houses to see evi¬ 
dence of this. The variegated Kail, to be found in any 
eottagei''s garden, proves the case as well as the most 
precious production of the tropics. In that plant it 
is manifest that the red, the white, the yellow, the 
other tints which harmonise so charmingly with the 
natural green of the leaf, are each dependent upon 
the veins, the universal symmetry of which has been 
so often pointed out. 
47. At the same time it must be admitted that there 
