DEVELOPMENT OF VEGETATIVE AND FLORAL BUDS 271 



esses. As Popham and Chang (1952) point out, dominance of the 

 apex disappears, for lateral flower buds and even inflorescence 

 branches are no longer correlatively inhibited, as were lateral buds, 

 by the vegetative apex. Moreover, if it is found that the central zone 

 plays a significant part in the biochemical division of labor of the 

 vegetative apex, then certainly the change in nature of the ceflular 

 components of this zone must imply a change in their function. Unless 

 this loss is compensated elsewhere, it may well prove true that the 

 loss of capacity for growth in length, the shift to the production of 

 reproductive axes instead of vegetative buds, and the loss of apical 

 dominance are concomitants of the change in visible structural pat- 

 tern. Presumably the effects of the leaf-produced "flowering hormone" 

 must include the initiation and promotion of these histogenic changes. 



SUMMARY 



In this investigation, the significant aspects of the inception of 

 flowering by photoperiodic induction must include the following asser- 

 tions: 



1 . The chain of events is repeated alike in short-day and long-day 

 plants. Whatever the inducing agent (or agents), it seems to be 

 capable of bringing about the same results in the different plants 

 investigated. The sample is small, but noteworthy. 



2. The zonation of the apex is affected similarly in all plants 

 studied. The central zone, envisioned by Buvat as the source of the 

 meristems from which arise inflorescences and flowers, cannot be so 

 interpreted in its changes by the present investigators. Rather, the 

 entire apical meristem becomes involved ultimately as floral induction 

 proceeds, more and more of the peripheral region of the apex produc- 

 ing floral leaves in single flowers or developing into an axis and bearing 

 bracts and floral buds in inflorescences. 



3. The elimination of a central zone and whatever biochemical 

 functions may be associated with it in the metabolic economy of the 

 apex undoubtedly is correlated with the fundamental set of changes set 

 into action by floral induction. The act of flowering therefore must 

 have as associated physiological changes at least the limitation of 

 growth of the apex, a changing phyllotaxy and loss of apical domi- 



