232 Transactions of the Boyal Microscopical Societij. 
shading a plant is quite another thing from so smothering it up as 
to cause it to become sickly and fade, or to prevent the develop- 
ment of young leaves by keeping them in the dark. In the 
instance above alluded to, the glare or heating properties of the 
solar spectrum were simply arrested from falling directly upon the 
leaves intended for analysis, by pieces of black cloth and small 
squares of very dark blue glass. 
Thus we see the effect of the constructive energy of light, 
which, simply speaking, means a greater percentage of chlorophyll, 
and an increase in the vitality of the plant. Reverse the experi- 
ment, and the opposite effect is most marked. That is to say, 
expose plants to the action of the red, yellow, or green rays of the 
solar spectrum, and they soon wither up, in consequence of the 
decomposition of the carbonaceous compounds through the destruc- 
tive action of light. Thus in ordinary daylight we have these two 
conflicting and contradictory agents combined, while we cannot 
fail to see in every-day life, how they affect the whole course of 
nature. It is, moreover, very curious how plants resist, as it were, 
this decomposing influence, and no doubt it is in this case greatly 
due to their colours not being in solution, though I do not 
wish to infer that it is so with all plants, for according to Kraus, it 
follows from his experiments that the green colouring matter is dis- 
tributed in such a manner in the colourless matrix of the chlorophyll 
grains that it must be considered in a state of solution ; they are 
therefore brought to a standard of equilibrium, which when reached, 
and having no more essential work to perform towards the process 
of their own development, or towards the economy of the plant to 
which they belong, excepting that of course of bearing, or helping 
to produce seed, are more quickly acted upon, so that we find the 
analysis reduces itself to a loss of 38 per cent, for chlorophylls, 
14 per cent, for orange xantliophylls, and 6 per cent, for mixed 
xanthophylls, &c. By comparing the figures in the subjoined table 
the whole subject will be seen at once. 
Exposed. Shaded. 
Gain per cent. Loss per cent. 
Chlorophylls 
.. .. 50 .. 
.. 09 
Xanthophylls 
.. 10 
Soluble in water . . 
.. .. 100 .. 
.. 
175 .. 
.. 79 
These experiments were all made with leaves from Acuba 
japonica, and their natural state was severally estimated as 
equalling 100. 
About the month of July, there was a most interesting article 
in ‘ Nature/ “ On the Source of the Carbon in Plants,” which no 
doubt many of you read at the time, and perhaps remember that it 
