388 University of Californw Publications in Botany [Vol.. ~> 



required in larger flowers. An attempt was made to get further data 

 on this point by removing the style several Jiours after application of 

 pollen before the pollen tubes could possibly have reached the ovary. 

 This operation occasionally causes the whole flower to fall, and since 

 in such cases abscission in the pedicel occurs before fall of the corolla, 

 no results in regard to the latter organ are obtained. The possible 

 effect of the operation on the abscission of the corolla was checked 

 by control tests of unpollinated flowers in which the styles had also 

 been removed. This can also be checked by a comparison with the 

 periods of. time given in table 1, column III. 



It was found in three flowers of t H179 that, when the style was 

 removed three days after pollination, the corolla was, on the average, 

 thrown off three days after anthesis. The control test for this experi- 

 ment gave in three flowers an average of five days. Where the style' 

 was removed two days after anthesis, four flowers gave an average of 

 three days. Where the style was removed one day after pollination, 

 the corolla was abscissed in five flowers an average of three days after 

 anthesis. A control test gave in this case an average of five days for 

 five flowers. Finally, the style was removed in seven flowers seventeen 

 hours after pollination. The seven flowers gave in this case an average 

 of four days for the time between anthesis and fall of the corolla. A 

 control test for this last case gave for five flowers an average of five 

 days. 



These experiments were repeated with N. sylvestris. In one case 

 where the style was removed in three flowers two days after pollina- 

 tion, the corolla was thrown off on an average of four days after 

 anthesis. A control test of this case gave an average of six days for 

 three flowers. In another case the style was removed in three flowers 

 one day after pollination. In this case the corolla was abscissed 011 

 an average of three days after anthesis. 



The results given in the above paragraphs indicate definitely that 

 it is the stimulation of stylar tissues caused by the growth of the 

 pollen tubes which shortens the time between anthesis and abscission 

 of the corolla. They also show that the removal of the style has no 

 appreciable effect on the abscission of the corolla. It is evident from 

 the results given that the influence of the pollen is seen as early as 

 seventeen hours after pollination, and it is possible that the effect may 

 be manifested even earlier. It is significant that the period given in 

 the case where the style was removed seventeen hours after pollina- 

 tion is one day longer than in the case where the style was removed 



