GRAFTING 83 



as a guide. In late summer bud grafting could be 

 done leisurely and with economy of bud material. 



Bud grafting in the fall has been largely a matter 

 of convenience at a time when the work might be 

 done leisurely, but there are certain fundamental 

 principles involved also. Water requirements are 

 small when the tree is resting from growth activities. 

 This lessens the danger from desiccation of the 

 graft. The operation of bud grafting stimulates 

 cambial activity locally for purposes of repair suffi- 

 cient for catching and holding a bud graft, but not 

 sufficient for catching and holding a scion graft of 

 the length commonly used until the new method of 

 grafting allowed us to use a scion of almost any 

 ordinary length in summer grafting. The shorter 

 the scion the better its chances as a rule, even with 

 the new procedure in late season scion grafting. The 

 bud graft and the scion graft shoot out buds 

 promptly until late in the summer. After that time 

 the bud graft remains dormant until spring and the 

 scion graft desiccates unless it is very short and 

 thickly paraffined. 



When a plant has been wounded in the course of 

 grafting or by accident repair will go on to some 

 extent at almost any time of the year, but callusing 

 for reparative purposes is most active in the spring 

 and early summer. This is no doubt due in part to 

 the degree of water pressure at that season if we 

 are to judge from the fact that in humid regions in 

 the tropics callus forms abundantly at any time. In 

 northern temperate regions scion grafting succeeds 



