84 Principles of Plant Culture. 



the formation of which, the stem and root increase in 

 diameter, originate in the leaves (67), the size and 

 firmness of the stem and the root depend somewhat 

 upon the number of leaves the plant bears. The more 

 leaves it has, the more solar energy it can transform 

 into plant tissue. The stem is larger beneath a vigor- 

 ous 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 eon- 

 tiuually perish through lack of light, have tall, but 

 very slender trunks, and their wood is soft because it 

 contains comparatively 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 ab- 

 sorbed by an immense number of leaves, develop mass- 

 ive 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 upright-growing plants, the leaves on the more 

 nearly vertical shoots are usually larger than those on 

 the horizontal 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 



