186 FUNDAMENTALS OF FRUIT PRODUCTION 



in the time when fruit buds are formed. A knowledge of the approximate 

 time when their differentiation occurs is of fundamental importance, 

 particularly in connection with possible means of influencing their number 

 by cultural treatment. Furthermore, the stage of advancement in which 

 the fruit buds enter the winter is shown elsewhere to have an important 

 relation to winter injury. 



For many years flower buds of the ordinary deciduous fruit trees 

 have been known, in a rather indefinite way, to have their inception in 

 the summer previous to their opening; more exact knowledge is compara- 

 tively recent and is even now rather incomplete. 



Investigation of the apple has been more extensive than is the case 

 with the other fruits; there is, however, enough similarity between them 

 to permit the use of the apple as the type. One difference, however, 

 between buds of apple and those of some of the other fruits, pointed out 

 elsewhere, should be borne in mind. The fruit bud of the apple is, with 

 trivial exceptions, a mixed bud, containing leaves and blossoms; in the 

 other type, as the peach, fruit buds contain no leaves. 



Evidence of Differentiation. — The growing point of the apple shoot or 

 spur presents a rounded surface surrounded by embryonic leaves and it is 

 characterized by its relatively large amount of meristematic tissue. 

 Sooner or later its aspect changes, taking one of two forms. 



In one case the change consists principally in the greater breadth of 

 the surface with a somewhat smaller degree of convexity and in the 

 absence of the swellings at the periphery that in the actively growing 

 shoot precede the formation of a rudimentary leaf. The amount of 

 meristematic tissue becomes relatively smaller. The growing point is 

 at the resting stage; surrounded by protective scales and embryonic 

 leaves, it constitutes the leaf bud. 



In the alternative case the growing point differentiates into structures 

 that form the essential part of the flower or fruit bud. The first evidence 

 of differentiation in this direction is the rapid elevation of the crown or 

 surface of the growing point into a narrow conical form, rounded at the 

 apex, with the fibro-vascular connections and pith areas advancing 

 concurrently. In the axils of the young leaves within the bud appear 

 other protuberances which soon become blunt at the top. At the same 

 time other leaf primordia develop rapidly higher in the spiral in which 

 they appear and in turn younger protuberances (the floral primordia) 

 appear in their axils. The apical protuberance, destined to become the 

 central (terminal) flower of the cluster, is differentiated last; however, 

 when it does take shape it is already larger than those previously laid 

 down. It soon takes and thenceforth maintains the lead in development 

 over the other flower primordia (see Fig. 24). 



Whether a bud which has entered the resting stage as a leaf bud, can, 

 without a renewal of growth, develop into a fruit bud later the same 



