THE FOOD OF PLANTS. 105 
the pleasure of knowing, without much chance 
of being far wrong, the age of the fallen trunk. 
So much for the changes that have taken place 
in this interval. The Winter’s sleep is again 
shaken off, and the tree begins to resume the 
duties of life. In a little while, the forest, which 
a short time since stood out all bare and rigid 
against the clear, sharp winter sky, becomes gra- 
dually clothed with leaves, and soon in such 
abundance that the eye can no longer penetrate 
as before into its inmost recesses. The voice of 
Spring to creation—Awake, sleepers, and live! 
has been heard over hill and dale, and all Nature 
has responded to the call, adorning herself with 
robes of living green,—coming forth as it were 
to salute the beloved season. 
Having in our last chapter glanced at the dif- 
ferent duties of the leaves, let us now spend a 
short time over those of the roots, and answer 
a few questions upon the Food of Plants. 
Some of our readers will perhaps say, Have 
we not already seen that plants feed on air, and 
obtain all their wood from the carbonic-acid gas 
mixed in the air,—what more do we require? 
True, but this is not all:—no! nor even, after 
