FRUIT-BUD FORMATION 61 



been abundant evidence of this fact, for when the trees are 

 defoliated by caterpillars, the following season the sap car- 

 ried much less sugar than usual. He also writes that, as the 

 leaf area varied from year to year, so the capacity to form 

 carbohydrates varied in proportion. It was further observed 

 that a tree standing in the open with well-developed 

 branches and large leaves produced more and richer sap 

 (4.39 per cent sugar) than those growing in dense brush 

 with small leaves (2.14 per cent sugar). 



55. Horticultural practices that influence fruit-bud 

 formation. — ^After it is recognized that the immediate 

 cause of fruit-bud dilTerentiation is within the tree itself, 

 the evidence of external factors related to such cause may 

 be considered. As in the case of the internal factors, it is 

 not possible to consider the external ones entirely individu- 

 ally, for they are closely inter-related. Several may bring 

 about a clear-cut response by the tree, either an abun- 

 dant formation of fruit-buds or excessive vegetative growth 

 and barrenness. 



Among the practices that may affect the tree in such a 

 way as to bring about fruit-bud formation may be listed the 

 following: cultural methods (using the tenn in a broad sense) ; 

 top- and root-pruning; ringing; grafting on slow-growing 

 stock (dwarfing); fertilizing and methods for controlling 

 insect and disease pests, thus protecting the foliage. Some 

 are special or extreme measures and are not ordinarily to 

 be recommended, while others are regular orchard opera- 

 tions. 



56. Cultural practices. — In Chapter VIII it is shown 

 that favorable soil conditions must be provided if maximum 

 commercial results are to be secured. Neither over- nor under- 

 vegetative trees are fruitful and obviously require dissimilar 

 treatment. In the case of trees which are growing too vig- 

 orously, it is probable that an abundant supply of nitrates 



