184 
THE PALE OP -THE (er ar 
OU know that in autumn nearly all the leaves fall 
from the trees. To be sure, a few trees (such as 
the pines and hemlocks) and some plants (such as the 
laurel and wintergreen and partridge vine) do hold fast 
their leaves all winter; but these are so few as com- 
pared with the many plants which lose their leaves, 
that they hardly count. 
Perhaps you never stopped to wonder why most 
plants get rid of their leaves before winter comes on; 
but you feel pretty sure now that there is some good 
reason for a habit that is adopted by nearly all the 
plants that live in this part of the country. 
When we were talking about the way in which 
leaves defend themselves from different dangers, we 
found that evergreen leaves, the leaves which hold fast 
to the tree and keep fresh all winter, manage to keep 
their water safe inside their cells by wearing a very 
thick skin, and by not having too many little leaf 
mouths. For when a leaf has a thin skin and a great 
many mouths, its water leaks away very quickly. And 
if many such leaves should remain upon a plant into 
the winter, might it not happen that they would let 
off all its water at a time when its roots could not find 
any more in the frozen ground? And thus might not 
the leaves kill the plant by draining it quite dry? 
So you can see why it is well for most plants to 
shed their leaves before winter comes on and the root's 
drinking water is turned into ice. 
