398 IOWA ACADEMY OF SCIENCE Vol. XXV, 1918 



From table IV it is seen tliat tlie difference between the per- 

 centag-es of g-ennination in the different concentrations is not so 

 marked at the end of long' periods as at the end of short periods. 

 In the long- periods there was time for many of the pollen grains 

 in the stronger solutions to secure the required amount of water 

 and germinate. In determining the most favorable solution for 

 germination, it is obvious that it is essential to consider the time 

 element. 



UNIFORMITY OF GERMINATION IN THE FIVE VARIETIES. 



All of the five varieties, excepting Duchess, have been re- 

 ported either partly or entirely self-sterile in the work of Lewis, 

 and Vincent (11). Self -sterility in some cases is loiown to be lo- 

 cal, and these varieties may not be sterile in the orchard at Iowa 

 State College. NeverthelevSs, it was thought worth while to in- 

 vestigate the uniformity of the water requirements of the five 

 varieties by using meanbranes which had given a more even and 

 a higher per cent of germination than th.e solutions. This was 

 aone by so\Adng the pollen of the five varieties on a piece of mem- 

 brane about 2 inches long and 1 inch wide, the pollen of each 

 variety o.ocupying a line running the full length of the niem- 

 brane. Table V gives the results obtained. 



TABLE V. 



PERCENTAGES OF GERMINATION AND GROWTH OF TLBES OF 



THE POLLEN OF THE FIVE VARIETIES UNDER 



SIMILAR CONDITIONS. 



Table V shows some variation in the germination of the pol- 

 len of the different varieties, but so little that all five can be 

 considered uniform in the water requirement for the germina 

 tion of their pollen. It is, therefore, obvious that self-sterility, 

 self-fertility and inter-fertility among these five varieties do not 

 depend upon a difference in the water requirement for the ger- 

 mination of their pollen. Some pollinating experiments were 

 carried on in the orchard to test out this assumption. For exam- 

 ple Jonathan, reported as entirely self -sterile by the Oregon Ag- 



