82 LIFE OF A TREE. 
of structure to this simple fact. Thus then 
the truth appears, that the vegetable world 
obtain all their strength, solidity, and size, 
from the decomposition of a gaseous ingredient 
in the viewless air. 
This function is principally confined to the 
leaves. Owing to some mysterious and peculiar 
power, the leaves are always drinking in carbonic- 
acid gas from the air. After its inhalation they 
have the power of condensing and decomposing 
it; and the result is, that they pour back all its 
oxygen gas, and retain all its carbon, out of 
which they then proceed to elaborate woody 
tissue. But this process of decomposition does 
not go on but under certain restrictions. Tor 
example, soon ‘‘as the evening shades prevail,” 
from the grass blade to the rustling raiment of 
the forest, all leave off work and cease to decom- 
pose carbonic-acid gas for the night. The red 
streak in the distant horizon, left by the down- 
sinking sun, tells the busy vegetable crowd its 
daily labour ’s done, and bids it fold its leaves to 
rest for the night. Obedient to the signal, the 
flowers fold up their painted petals, and droop 
the neck in the full attitude of rest. The leaves 
