46 LIFE OF A TREE. 
the leaves down to the roots, and brace up the 
plant, so that, even when it is a few weeks old, 
it is able to endure the angry buffetings of a 
very tempestuous wind. 
We must now proceed to take up again the 
thread of our history. Having watched the plant 
from the seed to the seedling, we have now the 
pleasant task of tracing out the characteristics 
of its growth. If we place the date of its birth 
in the Spring, the advancing year brings fresh 
strength and grace to the plant. During the 
warm days of Spring and early Summer, the 
number of its leaves, and its strength, stature, 
and diameter, all increase. On cutting across its 
stem at this early period, it would be found to 
be divisible only into two parts: a central portion, 
or pith, of cellular tissue; and an outer layer or 
skin. But as the leaves multiply, and the whole 
size of the plant becomes enlarged, the stem is 
greatly altered too. The woody bands, descend- 
ing from the leaves to the root, run between the 
bark or skin, and the pith, and consequently 
form a layer all around the pith, separating it 
from the bark: this layer much resembles a ring, 
and is called a concentric ring, or zone. Thus 
