1918] Kendall: Abscission of Flowers and Fruits in Solanaceae 389 



twenty-four hours after pollination. This may possibly indicate that 

 in the first case the influence of the pollen tubes has diminished, be- 

 cause of the shortening of the period which they have had for growth. 

 If this is the case, it is reasonable to suppose that the influence of the 

 growing pollen tube increases up to twenty-four hours after pollina- 

 tion as the pollen tube lengthens. Thus, at six hours after pollination 

 it is possible that no effect of the pollen tubes would be~ noticeable, 

 while twenty-four hours after pollination the entire influence of the 

 growing pollen tube has been exerted. 



The effect of pollination on the time between anthesis and flower- 

 fall was tested by experiments similar to those described above. 

 Results in such experiments are difficult to obtain because removal of 

 the style frequently causes the premature fall of the flower. If the 

 flower fell before abscission of the corolla, the fall was considered 

 premature, as the result of the removal of the style, and the record of 

 that particular flower not considered. Since under ordinary condi- 

 tions pollinated flowers remain on the plant, it is to be expected that 

 the stimulation of the stylar tissues by the pollen tubes, if it has any 

 influence at all, would increase the length of time between anthesis 

 and flower-fall. Granting the truth of this assumption, any reduction 

 in time between anthesis and fall can be considered as the result of 

 removal of the style. 



In one test on ten flowers of F x H179, where the style was removed 

 two days after pollination, flower-fall occurred on an average of seven 

 days after anthesis. A control test in this case also gave seven days 

 for ten flowers. This time is approximately the same (the actual 

 average calculated to the tenth of a day was 6.7) as those given in 

 table 1, column V, for the time between anthesis and normal flower- 

 fall due to lack of fertilization. A similar test on six flowers of N. syl- 

 veslris, where the style was removed two days after pollination, gave 

 an average of thirteen days. The time for this species in table 1, 

 column V, is fifteen days. > 



These two records indicate that the stimulation of the stylar tissues 

 by the growing pollen tubes has no effect on the time between anthesis 

 and flower-fall. In the second case above, and also perhaps in the 

 first, the stimulation of the style seems to have shortened the time 

 somewhat, but in this case the result can be explained by the effect 

 of the later removal of the style. 



