June, 1933] Pollination and Fruit Setting in the Apple 



11 



uJ-^^J^O^X 



A 



FiQ. 8 



B 



-a 



— a 



Fiq.9 



Fig. 7. End of pistil of Mcintosh (45x). a. Papilla-like terminal cells 

 of stigma, b. Pollen grain caught in terminal cells. 



Fig. 8. A. Pollen grains after absorbing water (270x). B. Pollen 

 grains before absorbing water (270x). 



Fig. 9. Pollen grains after three hours in germinating medium of 15 

 per cent sucrose (270x). a. Pollen tubes shortly after germination of 

 the pollen. 



shape but with a well-rounded surface which is somewhat roughened, enab- 

 ling it to adhere to the bodies of bees and other insects that visit the flowers. 

 Perhaps 75,000 pollen grains are produced by each vigorous, healthy 

 apple flower and all these could easily be carried on the body of a single 

 bee. Should each pollen grain from a single flower ultimately fertilize an 

 ovule, then the pollen from this one flower would be capable of causing the 

 setting of from 7,500 to 15,000 fruits, or the crop of 10 trees. What actu- 

 ally happens is that not more than one pollen grain in 10.000 ever reaches 



