FRUIT-BUD FORMATION 71 



fruit-buds which can be formed because of the reduction in 

 fruiting area, but even on the shoots which were produced 

 there was a preponderance of leaf-buds, apparently due to 

 shading. The knowledge on this subject is meager, however, 

 and there is need for additional research. 



It has recently been pointed out that the length of exposure 

 to sunlight is of the greatest importance in the growth and 

 development of plants, particularly with respect to sexual 

 reproduction. The following principle has been formulated 

 as a result of extensive experiments with a number of species: 

 "Sexual reproduction can be attained by the plant only 

 when it is exposed to a specifically favorable length of day 

 (the requirements in this particular varying widely with the 

 species and variety), and exposure to a length of day un- 

 favorable to reproduction but favorable to growth tends to 

 produce gigantism or indefinite continuation of vegetative 

 development, while exposure to a length of day favorable 

 alike to sexual reproduction and to vegetative development 

 extends the period of sexual reproduction and tends to 

 induce the ' ever-bearing' type of fruiting. " ^ 



67. Biennial bearing, — The biennial bearing habit of 

 fruit varieties has long been recognized and its solution 

 constitutes an important practical problem. It was formerly 

 considered to be an immutable varietal characteristic, but 

 this view has been radically changed and it is now regarded 

 as a nutritional problem. This conception is practically 

 nccessaiy inasmuch as there is no biennial-bearing commer- 

 cial variety which has not been shifted, in some instance, to 

 annual bearing through cultural means. That the problem 

 is nutritional seems evident, even though treatments ap- 

 parently the same have not brought about annual bearing 

 in all orchards of the same variety. It must be conceded, 



1 Garner, W. W., o.nd H. A. Allard. Jour. Agr. Res. Vol. 18, No. 11. 

 1920. 



