LEADING CHARACTERS. 
grows by additions to the interior and to the 
summit, in many genera not increasing in 
size with age. The progression of the tree 
is effected by the formation of fibrous matter 
at the base of the leaf, which on the decay 
of the latter is permanently added to the 
stem. 
The principal ditferences which accompany 
the structural distinction between Exogens 
and Endogens are that in Ihe latter (the 
barkless plants) the leaves are strait, and 
veined in parallel lines ; in the former, the 
leaves are more diversified in form, and the 
veins proceed from the central column. 
The seeds, as before noticed, are also differ¬ 
ent, and the distinct mode of branching 
and gro\Ath gives to each a separate cha¬ 
racter. 
The trees of our climate are exogenous, 
and so are the majority of our flowering 
plants and shrubs. The grasses, tree-ferns, 
sugar cane, palm, and plantain, are examples 
of endogenous vegetation. 
The ordinary exhibitions of the hydro¬ 
oxygen microscope, the more familiar dis¬ 
plays of less powerful magnifiers, and the 
