A two-year study indicated that, under orchard conditions, it takes 96 to 120 hours for pollen tubes to grow through the styles of almond flowers. In view of a rapid decline in receptivity, probably the result of embryo sac degeneration, it is assumed that the sooner the flower is cross-pollinated after opening, the greater the chance of fertilization and fruit-set.

Muriel V. Bradley, Pomologist in the Experiment Station, Davis, assisted with the microtechnical methods.