CUTTA GE. 



49 



direction ean be learned only by experience, but it may be said 

 that in general the hardest or closest wooded plants require a 



heel or a joint at the base. 

 Willows, currants, bass- 

 woods, and others with 

 like soft wood, emit roots 

 readily between the buds, 

 yet even in these cases pro- 

 pagators quite usually c u t 

 to buds. 



Wounds upon plants be- 

 gin to heal by the forma- 

 tion of loose cellular mat- 

 ter which gives rise to a 

 mass of tissue known as a 

 callus. This tissue eventu- 

 ally covers the entire 

 wound, if complete healing 

 results. As a rule, the first 

 apparent change in a cut- 

 ting is the formation of a 

 callus upon the lower end, 

 and it is commonly sup- 

 posed that this process 

 must be well progressed 

 before roots can form. 

 But roots do not necessarily 

 arise from the callus, and 

 in many plants they appear 

 to bear no relation to it 

 in position. In willows, 

 for instance, roots arise 

 from the bark quite irregu- 

 larly and at some distance 

 from the callus. Yet, as a matter of practice, best results are 

 obtained from callused cuttings, particularly if the cuttings are 

 made from mature wood, but this is probably due quite as much 



Fig. 44. Heel cutting of CornuS 



