TOP- WORKING SEEDLING PECAN TREES. 15 



Besides forming the regular wood of the tree, the cambium also grows 

 out over cut places and builds in woody tissues that heal over the wounds. 

 It is owing to this fact alone that budding and grafting are possible. 

 The callus on cuttings and root grafts is another evidence of the same 

 phenomenon, for the cambium of the roots of a tree is continuous and 

 identical with that of the branches. 



THE STOCK. 



The whole practice of successful grafting and budding is the proper 

 handling of active cambium. The cambium is the cementing material 

 that unites stock and cion, and unless there is active cambium there will 

 be no union. It must be said here that no matter how great the future 

 growth of the union, the cion never becomes truly united or fused with 

 the stock. The cambium grows all over and around the cut parts and 

 cements them together; but if the graft union be split open fifty years 

 later, the dead wood of the original cion may be found of the original 

 size and in the original position. Since, then, successful grafting de- 

 pends on the union of the cambium of the stock with that of the cion, 

 theoretically the best time for grafting and budding would be when the 

 cambium is most active. Actual nursery practice shows that this is 

 practically correct, at least as regards the stock. 



The ideal stock for propagation purposes is the young seedling of one 

 or two years growth. In such a stock all the tissues are new and fresh 

 and working to their maximum capacity, and the cambium is in its most 

 active condition. In top-working old trees it will be found that though 

 the branches may appear vigorous, they are a long way from having 

 anything like the active circulation found in small seedlings. Buds put 

 in these branches would give a very small "live," while the same care 

 on nursery seedlings could be counted on giving a high percentage of 

 living buds. In top-working, therefore, it is found necessary, in order 

 to get the cambium sufficiently active, to stub back the branches to mere 

 pollards. This cutting back should be done in the winter or dormant sea- 

 son. The following growing season will see a dense growth of very 

 vigorous shoots trying to repair the injury. See figure 1. These shoots 

 are ideal stocks, for, on account of their having all the sap from the 

 greater root of the mature tree, the cambium will be even more active 

 than in the nursery seedling. Often when nursery seedlings are in par- 

 tially dormant condition, owing to unfavorable weather or other con- 



