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Cross pollination


In connection with the mutual affinity of varieties which are selected for cross-pollination, there comes the question of the
"immediate influence" of pollen. For instance, if Seckel pollen is put on Kieffer pistils, will it impart the Seckel flavor, color and characteristic shape to the resulting fruit?

The characters of both may be united in the seeds, and the fruit trees which come from these seeds may be expected to be intermediates; but is the flesh of the fruit ever changed by foreign pollen? The increase in size which often follows crossing cannot be called a true immediate influence, for the foreign pollen generally stimulates the fruit to a better growth because it is more acceptable pistils, to the not because it carries over the size-character of the variety from which it came.

Setting aside the usual gain in size resulting from crossing, will there be any change in the shape, color, quality and season of ripening of the fruit? Most of the changes in fruit which are attributed to the influence of cross-pollination are due to variation. Every bud on a tree is different in some way from every other bud on that tree and may develop unusual characters, independent of all the other buds, according to the conditions under which it grows. The best way to determine whether there is an immediate influence of pollen is by hand crossing.

Most of the evidence supporting the theory that there is an immediate influence of pollen in the crosses of fruits comes from observation; most of the evidence against it comes from experiment. The observer, however careful, is likely to jump at conclusions; the exerimenter tries to give due weight to every influence which might ear on the problem. Since many observers and a few experimenters have found what seems to be an immediate influence of pollen on the fruit, it cannot be doubted but that this influence is sometimes exerted. But it is certainly much less frequent than is commonly supposed.

The distribution of the pollinizers
Having selected a pollonizer with reference to simultaneous blooming an 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 considered: 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 great fly modified 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 abundance 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.