"2. Certain of these varieties—Bing, Lambert, and Napoleon are mentioned especially—are inter-sterile. Mixed plantings of these three varieties cannot be expected to set fruit unless the trees are within the range of influence of some other variety or varieties that are inter-fertile with them.
"3. Among those studied, Black Republican, Black Tartarian, and Waterhouse seem to be the most efficient pollenizers for this group of varieties.
"4. Other good pollenizers that may be mentioned are: Elton, Wood, Coe, Major Francis, Early Purple. These, however, proved somewhat variable in their pollenizing abilities.
"5. Some of the seedling trees found in and about cherry orchards are efficient pollenizers for the three varieties—Bing, Lambert, Napoleon. Probably many of these seedling trees are efficient pollenizers, though the value of any particular seedling can be determined only by experiment or very careful observation.
"6. At least some members of the Duke group of cherries are capable of pollinating some of the Bigarreaus.
"7. At least some of the varieties of the Sour Cherry (P. cerasus) are capable of pollinating some of the Bigarreaus.
"8. Inter-sterility of Sweet Cherry varieties is apparently not correlated with their closeness of relationship.
"9. The ability of a variety of cherry to set fruit is not entirely dependent upon the kind of pollen available. Environmental factors are important."
It is doubtful if New York cherry-growers will need to pay much attention to cross-pollination but, in case cherry trees are not setting full crops, and for no other apparent reason, the fertility of the blossoms may well receive attention. Should varieties be found self-sterile, sorts must be chosen which come into blossom at the same time, in which case the preceding table shows the sorts which bloom together or nearly enough so to make cross-pollination possible.