LEAVES, BUDS AND FLOWERS 77 



The more leaves it has, the more solar energy it can trans- 

 form into plant tissue. The stem is larger beneath a 

 vigorous leafy branch, and if cut off some distance above 

 a branch, the part thus deprived of its foliage ceases to 

 grow, unless it develops new leaves. Trees growing in 

 the dense forest, where their lower branches continually 

 perish through lack of light, have tall, but very slender 

 trunks, and their wood is soft because it contains com- 

 paratively little fibrous tissue, while other trees of the 

 same species in the full light of the open field, through 

 the large amount of solar energy absorbed by an immense 

 number of leaves, develop massive trunks, of which -the 

 wood, being packed with fibrous tissue, is much stronger 

 than that of the forest tree. 



124. The comparative size of leaves on a given plant 

 depends much on the water supply during their formation. 

 The leaves of sap-sprouts (223), that take an undue 

 proportion of water, are usually very large, and in up- 

 right-growing plants, the leaves on the more nearly 

 vertical shoots are usually larger than those on the hori- 

 zontal ones. The more vigorous the plant, the larger, 

 as a rule, are its leaves, and the softer is its woody tissue. 



In plants grown from seed to secure new varieties, 

 large leaves may be taken as evidence of superior root 

 development, which implies capacity to endure drought 

 and, therefore, hardiness. In the apple, the large-leafed 

 varieties are, as a rule, hardier than others, probably 

 because their vigorous roots supply the needed water 

 during the dry season, thus enabling the tree to mature 

 healthy wood and buds which can pass severe winters 

 unharmed (174). 



Crops grown for their leaves, as cabbage, lettuce, to- 

 bacco and the like, are especially liable to be curtailed 



