18 QUINCE CULTtTRU. 



cut back or broken off by accident, or when even the 

 whole head of the tree has been removed. In a very vig- 

 orous tree it is quite common to have the buds push 

 their threefold development simultaneously; the central 

 growth bearing the blossom, and those on either side of 

 it only making wood-growth. Occasionally two of the 

 three bloom together. By observing the position of 

 the buds along a branch, in going the length of five buds 

 you can so prune as to give any desired direction to the 

 new growth, and thus form a symmetrical tree. 



*The leaves, with their stipules, form the foliage of the 

 tree, and seem to serve much the same purpose for it that 

 the lungs of animals do for them. Leaves not only give 

 beauty to the tree, but are necessary to its existence. 

 They are formed of a series of veins, between which is 

 the cellular tissue or parenchyma, which consists of 

 numerous cells of various forms, with air spaces between 

 to increase the surface exposed to the air and sunlight. 

 There are about 25,000 of these breathing pores in each 

 leaf, through which moisture and air are received, and 

 vapor and carbonic acid given off. By this process the 

 sap in the leaves is thickened, and the material of woody 

 fiber elaborated. The wood of trees is chiefly carbon, 

 which the leaves have absorbed from the air. Their ni- 

 trogen comes from the combined influence of the air, the 

 sun's light and heat, the humus of the soil, and the action 

 of potash. Analysis of the ashes shows that a very small 

 part of the constituents come from the soil. The air 

 is an abundant storehouse of exhaustless capacity, full 

 of the materials of plant growth, to which each culti- 

 vator possesses a key. Every man and air-breathing 

 animal on earth is helping to keep this atmospheric 

 storehouse filled with the material of plant growth 

 by every breath exhaled ; and so all animated creation 

 is at work for the tiller of the soil. Not only are 

 the leaves the laboratory of the growing wood, but 



