102 LIFE OF A TREE, 
wood and intervening parts. The ring nearest 
the pith was formed in the first year of the life 
of the tree, and every succeeding year leaves its 
mark in the addition of a ring for each, composed 
of the wood formed during the year by means 
of the leaves. 
It is necessary however to say, that there is 
a large division of 
trees and plants in 
which these rings 
will not be found,— 
such, for instance, 
Pa: as 
as the sugar-cane, 
the palm-trees, and 
many more. These 
trees are also differ- 
ent from such trees 
as apple and oak- 
trees, in that their 
leaves are marked 
with straight lines instead of like a net-work, 
as will be noticed if we examine an oak-leaf. 
These differences are also shewn in the cut. 
The trees marked with the rings are called ex- 
ogenous or dicotyledonous trees; those merely 
SECTION OF AN ENDOGEN, 
