The Orchard Plant 57 



for stems at all? The only purpose they serve is to lift 

 the leaves up to those situations where they will receive 

 the maximum amount of sunshine and of air. In its 

 natural state the grapevine could best do this with the 

 support of other plants. It can now easily reach the tops 

 of tall trees, and is thus enabled to flourish in situations 

 where it would otherwise perish. On the other hand, the 

 dandelion has so successfully adapted itself to conditions 

 that it has become a most persistent weed, and yet it is 

 nearly stemless. 



But the crude food materials taken in by the roots must 

 pass through the stems or trunk to the leaves, and a por- 

 tion of elaborated food must be returned, even to the 

 smallest root, to build up the parts. The trunk must 

 therefore be kept in a healthy, vigorous condition, and a 

 knowledge of its make-up will help one to a more thorough 

 understanding of some of the important horticultural 

 operations. 



A good idea of the make-up of such a stem as is found 

 among orchard trees may be had by consulting the dia- 

 gram shown in Figure 6. This represents a plant or a stem 

 at the close of the first season's growth. Older trunks or 

 branches would present much the same appearance, with 

 the exception that there would be as many layers of wood 

 as there were years of growth, and the parts would be 

 more compact. 



The central portion of the stem at 1 is composed of pith. 

 This was originally formative tissue, and out of it the other 

 special cells are formed. The pith may serve as a storage 

 for plant-food, but as the plant becomes older, these cells 

 gradually lose their function. 



