84 



PRINCIPLES OF PLANT CULTURE 



attention than is due to it. Two principles may be 

 cited, however, which if they do not explain all phe- 

 nomena connected with the formation of flower-buds, 

 are of sufficient general application to have great eco- 

 nomic value, viz. : Plants form flower-buds only when they 

 contain reserve food (84) ; water supply insufficient for 

 rapid growth may suffice for abun- 

 dant food formation (59). 



In support of the first of these 

 propositions, we mention : (a) Rap- 

 idly-growing plants rarely form 

 many flower-buds, because the food 

 is used up in growth as fast as 

 formed, (b) Checking such rapid 

 growth, by removing the growing 

 points of the stem or root (67), 

 or by withholding water, results 

 in an accumulation of food and 

 is often followed by an abundant 

 formation of flower-buds, (c) Ob- 

 structing the rootward current of 

 prepared food (79), as by " ring- 

 ing" (416) causes an accumulation 

 of food above the obstruction and 

 is often followed by the formation 

 of flower-buds in that part. 



In support of the second propo- 

 sition we mention : (a) Florists 

 often bring their plants into bloom at a desired time 

 by withholding water. (b) The flower-buds of most 

 out-door plants are formed during the drier part of sum- 

 mer (plants that live over winter and bloom in spring, 

 as the apple, strawberry and the like, form their flower- 



FIG. 43. Fruit-spurs of 

 the apple. A points 

 at which apples were 

 detached the preced- 

 ing year; W wrinkles 

 marking points at 

 which leaves were de- 

 tached in previous 

 years. 



