152 HORTICULTURE, FORESTRY, FLORICULTURE 



mediate influence of pollen in the crosses of fruits comes from obser- 

 vation ; most of the evidence against it comes from experiment. The 

 observer, however careful, is likely to jump at conclusions; the ex- 

 perimenter tries to give due weight to every influence which might 

 bear on the problem. Since many observers and a few experiment- 

 ers have found what seems to be an immediate influence of pollen 

 on the fruit, it cannot be doubted but that this influence is some- 

 times exerted. But it is certainly much less frequent than is com- 

 monly supposed. 



The Distribution of the Pollinizers. Having selected a pol- 

 linizer with reference to simultaneous blooming and mutual affinity, 

 the fruit farmer will wish to know how many trees will be necessary 

 to pollinate the self-sterile variety. There are three things to be con- 

 sidered: the ability of the pollinizer to produce pollen, its market 

 value, and the class of fruit to which the self-sterile variety belongs. 



Varieties differ in the amount of pollen which they produce, 

 and the pollen production of the same variety is also greatly modi- 

 fied by differences in locality and season. Other things being equal, 

 the variety which produces pollen freely could be used more sparingly 

 in a block of self-sterile trees than one of scanty pollen production. 

 As a matter of fact, most of our common varieties produce an abun- 

 dance of pollen. The number of trees of the pollinizer would also 

 depend largely on whether it has value in itself. Some growers 

 plant every tenth row to the pollinizer, but the proportion should 

 usually be greater. This might be enough if the weather during the 

 blossoming season is very favorable for cross-pollination by wind and 

 insects ; but if it is showery, the pollinizers should be more abundant, 

 in order that cross-pollination may be more general during the bright 

 weather between showers. In a commercial orchard, the pollinizer 

 should be planted in a solid row. Theoretically, it is- much better 

 to have the pollinizer more evenly distributed among the self-sterile 

 trees; practically, it will not pay to so mix them except in small 

 orchards. 



Advantages of General Mixed Planting. Cross-pollination 

 gives better results with nearly all varieties, be they self-sterile or self- 

 fertile. A variety may be able to bear good fruit when it is planted 

 alone, but it will often bear better fruit if suitable varieties are near it. 



Mixed orchards are more productive than solid blocks, taking 

 the country over. It is a common observation in Western New York 

 that Baldwins in mixed orchards are more uniformly productive 

 than Baldwins in large blocks. Furthermore, although a variety 

 may be able to set an abundance of fruit with its own pollen, this 

 fruit will often be smaller than if other pollen were supplied. 



The Pollen-Carriers. The pollen of one variety is carried to the 

 pistils of another in two ways: by the wind and by insects. There 

 are many kinds of insects which aid more or less in the cross-pollina- 

 tion of orchard fruits, principally bees, wasps and flies. Of these, the 

 wild bees of several species are probably the most important. In a 

 wild thicket of plums or other fruits, they are usually numerous 

 enough to insure a good setting of fruit. But few if any wild bees 



