NUTRITION AND GROWTH OF PLANTS. 



soms and fruits, more nourishment from the air 

 than it can afford, and consequently they will not 

 reach maturity. In many cases the nourishment 

 afforded by the air under these circumstances suf- 

 fices only to complete the formation of the leaves, 

 stems, and branches. The same result then ensues 

 as when ornamental plants are transplanted from 

 the pots in which they have grown to larger ones, 

 in which their roots are permitted to increase and 

 multiply. All their nourishment is employed for 

 the increase of their roots and leaves ; they spring, 

 as it is said, into an herb or weed, but do not 

 blossom. When, on the contrary, we take away 

 part of the branches, and of course their leaves 

 with them, from dwarf trees, since we thus prevent 

 the development of new branches, an excess of 

 nutriment is artificially procured for the trees, and 

 is employed by them in the increase of the blossoms 

 and enlargement of the fruit. It is to effect this 

 purpose that vines are pruned. 



A new and peculiar process of vegetation ensues 

 in all perennial plants, such as shrubs, fruit and 

 forest trees, after the complete maturity of their 

 fruit. The stem of annual plants, at this period 

 of their growth, becomes woody, and their leaves 

 change in colour. The leaves of trees and shrubs 

 on the contrary remain in activity until the com- 

 mencement of the winter. The formation of the 

 layers of wood progresses, the wood becomes harder 

 and more solid, but after August the leaves form no 



