198 REPORT OF STATE BOARD OF HORTICULTURE. 



The poor setting of fruit, which often follows a long- pain and sometimes a 

 shower, is due more to a loss of vitality in the pollen or to some mechanical 



injury to the pistils: also, in large measure, 

 to the fact that bees and other insects which 

 promote the beneficial cross-pollination be- 

 tween varieties are absent. If the rain lasts 

 for several days, the pollen may lose its vi- 

 tality. After a week of rainy weather at 

 Ithaca, in the spring of 1898, nearly all the 

 pollen of the apricots then in bloom was dis- 

 organized and stuck together, so that it could 



7.S.— Pollen injured by rain. Much not possibly grow and fertilize the pistils. 

 magnified. " Compare Fig. 80. g^^^ ^^ ^^.^ ^^^^^^ .^ ^^^^^ .^ j,.^_ ^g_ ^^ .^ 



also natural to suppose that a hard rain may wash off, dilute, or otherwise 

 injure the juices of the stigma so that the pollen cannot germinate after it 

 falls upon the stigma. Perhaps a long "spell" of wet weather may even kill 

 the pistils after they have been fertilized. 



Thus a rain during the blooming season may decrease the setting of fruit 

 in four ways : (1) By preventing the pollen from reaching the stigma, both 

 because it is too wet to fly and because pollen-carrying insects are absent. 

 This is imiDortant only when the rain lasts several days and most of the 

 pistils pass their receptive state before the rain ceases. i2) By destroying- 

 the vitality of the pollen. (3) By injuring the stigma. (4) By preventing- 

 fertilization or the germination of the pollen because of low temperature. 



THE BLOSSOMS MAY BE INJURED BY STRONG OK DRYING W^INDS. 



Near the sea and large lakes, fruit blossoms may be whipped off by very 

 severe winds. In such cases a mixed windlireak of deciduous and evergreen 

 trees may be used to advantage. Drying winds during the blossoming season 

 are not common in the east, but are often serious in some parts of the west. 

 Luther Burbank, one of our best observers and experimenters in orchard 

 pollination, says a dry wind sometimes causes a short fruit crop in some })arts 

 of California by drying up the juices of the stigma so that the pollen cannot 

 germinate. 



II. SELF-STERILITY. 



There have been described in the preceding pages some of the influences 

 which decrease the setting of fruit. These were mentioned only to make 

 more clear a talk about self-sterility, an influence which is second only to 

 the winter injury of fruit buds in the loss caused to the commercial fruit- 

 grower. Since the loss from unfavorable weather usually cannot be pre- 

 vented, while the loss from self-sterility can, in a large measure, the latter 

 subject deserves more than the brief notice which has been given to the 

 former at this time. 



There are some trees which blossom full year after year, but set little 

 fruit, even in the most favorable seasons. These trees are usually in solid 

 blocks, or at a distance from any other variety. Planting near them other 

 trees of the same variety does not make them fruitful: but if trees of other 



