504 



FUNDAMENTALS OF FRUIT PRODUCTION 



in the tomato. To what extent premature pollination interferes with 

 the set of fruit in the orchard is unknown. 



Table 2. — Influence op Premature Pollination on Setting in Tobacco 

 {After Hartleif^) 



It is well known that if pollination is long delayed the blossoms fall without 

 setting. Kusano/'' working with orchids belonging to the genus Gastrodia, found 

 that when pollination was delayed for 2 to 3 days fertilization took place in an 

 almost normal manner. When it was delayed 4 days it was rather ineffective 

 and when it was effective the resulting fruit varied in size "according to the 

 number of embryogenic seeds." He also made the interesting observation that 

 when pollination was delayed 3 to 4 days a comparatively large percentage of 

 the seeds formed were poly embryonic, while seeds resulting from earlier pollina- 

 tion seldom contained more than one embryo. 



Nutritive Conditions Within the Plant. — There is abundance of 

 both circumstantial and experimental evidence to show that the nutri- 

 tive conditions within the plant at and just after the time of blossoming 

 are important in determining the percentage of the blossoms that will set 

 and also the percentage that will finally reach maturity. 



Effect on Pollen Viability. — Sandsten"* collected pollen from old 

 apple trees in a poor state of vigor and at the same time from strong young 

 trees of the same varieties in an adjoining orchard. The average percent- 

 age germination of the first lot was 39.8 while that of the second lot was 

 56.5. The average number of hours required for germination of the pollen 

 from the strong trees was 19.8 ; for that from the weak trees, 28.7. Though 

 these differences may not be great enough under average conditions to 

 account for much failure to set fruit, it is conceivable that they may 

 be of real importance under some conditions. Furthermore, it is possible 

 that greater differences frequently exist between the pollen of strong and 

 weak blossoms of other varieties and of other fruits. 



Effect on Defectiveness of Pistils. — Goff^^ reported the percentage 

 of defective pistils borne by trees of the American varieties of plums and 

 consequently their fruitfulness to be closely correlated with nutritive 

 conditions within the tree. Exhaustion or weakening one season by 

 overbearing, drought or poverty of soil was found to induce the production 

 of many defective pistils the following spring. He suggested thinning as 



