837 



equally distant from the centre as in an ungrafted or unbudded trunk, but at 

 z and cc shows a deep depression, an S-like curvature. This curved line of 

 union, G dp pert' s "line of demarcation," is visible to the naked eye and is 

 noticeable even in the bark covering\ 



In the second, usual method of budding "with a heel," the bud is cwf/rom 

 the branch with a little piece of wood attached and is shoved into the stock. 

 In this the processes of healing vary somewhat from those described above. 

 The disadvantage in this method is a retarding of the union; the advantage, 

 however, lies in the increased certainty of preserving the bud. In separating 

 the bark shield from the wood body, 

 for the purpose of bark budding, the 

 actual bud cone is not infrequently left 

 on the branch if its vascular bundle 

 cylinder has been too greatly lignified. 

 The bud on the bark shield then has a 

 hole on its underside and does not 

 sprout. Untrained workers overlook 

 this little hole and bud in vain. 



The same process of healing, as in 

 budding with a heel, is found in hark 

 grafting. Only in this case the stock is 

 more injured since it must first be cut 

 square off, then the bark on one side is 

 split and somewhat raised for the in- 

 sertion of the scion as is done in bud- 

 ding. Instead of the single eye a diag- 

 onally cut branch is used, bearing 

 several buds. The slanting cut surface 

 forms simple overgrowth edges, i. e. 

 fixed wound-walls, which unite with 

 the mobile wound-walls of the bark 

 strips of the stock and the uniting tis- 

 sue of its exposed wood surface. In 

 bark grafting {"whip grafting"), how- 

 ever, the stock has more to do and 



stores up less reserve plastic material, since the part of the cross section on 

 the end surface of the stock not covered by the scion must also be overgrown. 



The luxuriance, to which the process of coalescence can attain in bark 

 grafting on strong stock, is shown by the accompanying drawing (Fig. 200), 



nl- 



Fig-. 200. 



Bark graft of Aesculus, with 

 adventitious buds. 



1 The difference between the pre.sent experiments and previous worlt lies in the 

 proof of the different origin of the tissue of union or, according to Goppert, the "inter- 

 mediary cell tissue." He thinks that tlie production of the tissue which, in common 

 with the cambium, takes over the coalescence, must come from the medullary rays, 

 while Hanstein considers the whole tissue of union to be produced by the cambium 

 alone. Actually, all elements, still capable of new formation, can take part in the 

 formation of the wound callus and tissue of union. In many ti'ees, for example, 

 good instances of wound callus may be obtained which is formed from the pith 

 body, particularly the pith crown. (Tilia.) 



