120 THE NURSERY-MANUAL 



In the season of greatest growth it usually occurs as a soft 

 mucilaginous and more or less unorganized substance, and in 

 this stage it most readily repairs and unites wounded surfaces ; 

 and for this reason the grafting and budding of old trees are 

 usually performed in the spring. Later in the season, the 

 cambium becomes firmer and more differentiated, and union 

 of woody parts is more uncertain. 



It is necessary to cover the wounds to check evaporation 

 from the tissues. In outdoor work, wax is commonly used 

 for all kinds of grafting that wound the wood itself, but in 

 budding, the loosened bark, bound down securely by a bandage, 

 aifords sufficient protection. It is commonly supposed that 

 an ordinary cleft-graft cannot live if the bark of the stock 

 immediately adjoining it is seriously wounded, but the bark 

 really serves little purpose beyond protection of the tissues 

 beneath. A cion will grow when the bark is mostly removed 

 from the stub, if adequate protection is given which will not 

 interfere with the formation of new bark. 



The cion must always bear at least one good bud. In most 

 cases, only buds that are mature or nearly so are used, but in 

 the grafting of herbs very young buds may be employed. 



These simple requirements may be met in an almost innumer- 

 able variety of ways. The cion or bud may be inserted in the 

 root, crown, trunk or any of the branches ; it may be set simply 

 under the bark, or inserted into the wood itself in almost any 

 fashion ; and the operation may be performed either on grow- 

 ing or dormant plants at any season. But in practice there 

 are comparatively few methods sufficiently simple and ex- 

 peditious to admit of general use ; the operator must be able 

 to choose the particular method best adapted to the case in 

 hand. 



