64 
gealed by cold, and certainly not so easy of de- 
composition ; and their vessels are defended by 
stronger coatings from the action of the elements. 
The production of the other parts of the plant 
takes place at the time the leaves are most vigor- 
ously performing their functions. If the leaves 
are stripped off from a tree in spring, it uniformly 
dies, and when many of the leaves of forest trees 
are injured by blasts, or long-continued dryness, 
the trees always become stag-headed and unhealthy. 
The leaves are necessary for the existence of 
the individual tree, the Jiowers for the continuance 
of the species. Of all the parts of plants they 
are the most refined, the most beautiful in their 
structure, and appear as the master- work of nature 
in the vegetable kingdom. The elegance of their 
tints, the variety of their forms, the delicacy of 
their organization, and the adaptation of their 
parts, are all calculated to awaken our curiosity, 
and excite our admiration. 
In the flower there are to be observed, 1st, the 
calyx, or green membranous part forming the sup- 
port for the coloured floral leaves. This is vas- 
cular, and agrees with the common leaf in its tex- 
ture and organization ; it defends, supports, and 
nourishes the more perfect parts. 2d, The corolla , 
which consists either of a single piece, when it is 
called monopetalous, or of many pieces, when it 
is called polypetalous. It is usually very vivid in 
its colours, is filled with an almost infinite variety 
of small tubes of the porous kind ; it incloses and 
defends the essential parts in the interior, and sup- 
