PRUNING 221 



grown in the light. Thus many forest trees which have short, 

 thick, and much branched trunks, when growing in pastures, grow 

 tall slender stems with branches only at their tops when grown 

 in forests where they are much shaded. It is for this reason that 

 most forest trees grow trunks more valuable for lumber when 

 grown in thick stands. (Figs. 199 and 200.) This principle is 

 observed in growing Sorghum and Corn chiefly for fodder, in which 

 case the plants are grown in thick stands, so that their stems will 

 be finer and, therefore, better for feed. Such a response to shade 

 is often an advantage to plants, for it is through the elongation 

 of their stems that plants compete for light by endeavoring to 

 raise their leaves above the shade of neighboring plants. 



Also the development of stem tissues is more or less influenced 

 by light. Stems grown in diminished light do not have their 

 mechanical tissues so well developed. For example, when grain 

 plants receive insufficient light on account of being much crowded, 

 they have commonly weak stems and are likely to lodge. The 

 bast fibers of flax are finer when the plants are thick on the 

 ground, and when flax is grown for fibers it is commonly grown 

 in thick stands. 



Pruning 



Pruning consists in cutting away portions of the plant and is 

 done for reasons too numerous for more than a few to be men- 

 tioned here. 



First, trees that tend to grow tall and slender may be induced 

 to acquire a low thick top by subjecting them to the process called 

 "heading-in," which consists in pruning the main branches so that 

 growth in height is checked and a good development of lateral 

 branches is induced. This method is often used in controlling 

 the shape of shade and fruit trees. It is by this means that hedges 

 are made to grow low and dense and thus capable of turning stock 

 when used for fences. 



Second, often, as in case of fruit trees, pruning has for its pur- 

 pose the checking of growth which has been so thoroughly ex- 

 hausting the food supply as to result in a shortage of fruit buds. 

 In this case growth is checked by removing the terminal buds 

 from the leaders and the food supply thereby conserved. 



Third, plants are sometimes pruned to delay maturity. For 

 example, in growing Sweet Peas the young pods are pinched off 



