452 PEACTICAL BOTANY 



made by pruning is small, the cambium layer sometimes grows 

 over the cut surface, the wound thus healing without becom- 

 ing the place of infection. But large wounds are almost cer- 

 tain to become infected with fungus spores before they heal, 

 and they thus become the means of injury or destruction of the 

 whole plant. A heavy coat of paint placed upon the cut sur- 

 face usually prevents the entrance of destructive organisms. 



At transplanting, all injured roots are pruned away and new, 

 vigorous roots are soon developed. During the time when the 

 roots -are becoming established, transpiration of water from 

 the aerial parts may greatly endanger the plant. This is one 

 of the reasons for heavy pruning of the top at the time of 

 transplanting. After the top has been pruned new growth 

 develops, and by the time the root system is established and 

 is thus in position to take up water, the increased transpiring 

 surface produced by the new growth may be supplied with 

 water. When transplanting potted plants into the garden it 

 is often necessary to cover or otherwise protect them against 

 excessive transpiration until the roots are established. This 

 serves the same purpose that pruning does in transplanting 

 woody plants. Indeed, succulent potted plants are sometimes 

 pruned when they are transplanted. 



Pruning for better form is extensively practiced in caring 

 for the shrubs and trees of lawns and parks. By pruning to 

 determine just what part of a plant may develop, almost any 

 desired form may be produced. In this way apple trees have 

 been made to grow as vines, roses have been made to grow 

 like box hedges, and grapevines have been made into upright 

 and self-supporting shrubs. 



In pruning for better flowers and fruit, only a comparatively 

 small number of vigorous buds or branches are permitted to 

 grow. In this way each bud which grows receives proportion- 

 ately much more nourishment from the whole plant than 

 would be true if all the parts had remained. If all but one or 

 two of the flower buds of a tomato plant are pruned away, 

 larger and better fruit is produced. Chrysanthemums and 



