LEAVES, 29 



trary, wlien rapid and vigorous vegetation is 

 checked, blossom-buds, and consequently, fruit 

 will be in abundance — thus, fruit is seldom 

 borne on the thick vigorous shoots of the 

 peacli, &c., but generally on the slender ones. 



If an unproductive tree is transplanted, it often 

 becomes productive from the check given. 



In India and China, trees are brought to bear 

 fruit by cutting the roots or exposing them to 

 dryness. 



Leaves. 



Leaves are expansions of bark, traversed by 

 veins. 



The veins consist of spiral vessels enclosed 

 in woody fibre ; they originate in the medullary 

 sheath and liber; and they are connected by 

 loose cellular tissue which is full of cavities 

 containing air. 



This cellular tissue consists of two layers, of 

 which the upper is composed of small cells 

 perpendicular to the outer skin, and the lower 

 of small cells parallel with the outer skin. 



These small cells are arranged so as to 

 leave numerous open passages among them 

 for the circulation of air in the inside of a 

 3* 



