THE FLOWKK BEHAN'IOR OF AVOCADOS 



159 



There is then an opportunity for close-pollination. When a set 

 of floAvors skips the first j^eriod and has a single openin*^- during 

 which pollen is shed, there would seem to be opportunity for self- 

 fertilization of individual flowers provided the pistils have re- 

 mained receptive to the pollen. There is, however, some ques- 

 tion as to what extent off-stride flowers can function in fertiliza- 

 tion and fruit-setting. 



The variations in blooming due to influences of weather and 

 the time of the season no doubt liave an effect on pollination 

 relations and on the efficiency of pollinations in the setting of 

 fruit. Growers frequently state that often the fruit borne by 

 avocados is set late in the period of bloom. 



The regulation of the flower mechanism 



It seems evident that the principal external stimuli affecting 

 the flower mechanism of avocados are light and temperature. 

 The rule is that during normal action the flowers are open only 

 during the hours of daylight. Changes in temperature, how- 

 ever, produce marked irregularities in the action of the flowers 

 irrespective of light. 



The influence of lo^v temperatures was tested by submitting 

 branches with flowers to the cool temperatures of an ice-box. 

 Under such treatment flowers that were fully open remained 

 thus for hours after flowers of the same set left on the trees had 

 closed. Meanwhile flowers in the interval between the two open- 

 ings remained closed while those of the same set left on the tree 

 opened normally. Low temperatures seem to inhibit changes in 

 flowers as may be expected from the observations on off-stride 

 and irregular behavior. 



Clusters of flowers were placed in an ice-box during the mid- 

 day shift of sets when first-period flowers were in process of 

 closing and when second-period flowers were about halfway 

 open. In several instances the action of these two sets w^as 

 stopped and reversed. The first-period flowers returned to the 

 condition of being widely open and the second-period flowers re- 

 turned to the fully closed condition. An extension of such 

 studies would no doubt reveal much regarding the influence of 



