Seeking Aid of the Bee
The method of pollenating on a large scale sometimes employed by Mr. Burbank is to place a branch of wild cherry blossoms, as shown in this picture, on a cultivated tree. The bees will then effect cross-pollenation, and the virile qualities of the wild cherry will be introduced into the strains if the cultivated ones. As in the case of the hybrid plums, the offspring of later generations may manifest the good traits of both ancestral strains in combination.
This image is from: Luther Burbank: his methods and discoveries and their practical application. Volume 2 Chapter 7