FLORIDA STATE HORTICULTURAL SOCIETY 



81 



flower, 24 or more hours before the pol- 

 len of that flower is shed, obviously 

 makes self-fertilization of individual flow- 

 ers impossible. 



In a report concerning' avocado cross- 

 pollination made in Florida during April 

 1916 for the U. S. Department of Agri- 

 culture mention was made of the opening 

 of two sets of flowers each day, one in the 

 morning and the other in the afternoon. 

 Many points concerning avocado flowers 

 and their behavior were recorded in this 

 early report. Had individual flowers been 

 tagged to better observe their behavior, 

 the differences in them during the two 

 open-periods of each flower, with the in- 

 tervening closed period, would no doubt 

 have been discovered at that time. 



Close-pollination is also greatly re- 

 stricted. The possibility of pollen being 

 carried from a flower shedding pollen to a 

 first-period flower of the same tree (inter-' 

 period close-pollination) is most decidedly 

 limited. The rule of behavior is that 

 only flowers of the same period-opening 

 occur together on a tree at one time. 



Thus during the entire forenoon only 

 first-period flowers will be found open on 

 a tree of Taylor. About noon these flow- 

 ers close fully and another set of flowers 

 will open for the second time, and this is 

 a set that opened for their first-period on 

 the forenoon of the previous day. Dur- 

 ing the afternoon these flowers shed pol- 

 len. They are unable to self -pollinate 

 properly for their pistils were most ready 

 to receive pollen some 28 hours before. 

 There are no first-period flowers open on 

 the tree to which their pollen can be 

 carried. This daily alternation in the 

 character of the flowers occurs day after 



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day with such precision that the chances 

 for proper cross-pollination are indeed 

 slight. The tree is really female in the 

 forenoon and male in the afternoon! 



A tree of Panchoy may be growing by 

 the side of the Taylor tree. Observations 

 of its flower behavior will reveal a daily 

 periodicity or alternation of the sets that 

 is exactly the reverse of that in the bloom- 

 ing of Taylor. During the forenoon 

 only second-period flowers are open. 



During the afternoon only first-period 

 flowers are open. Thus the tree is male in 

 the forenoon and female in the afternoon. 

 Itsi flowers are unable to self-fertilize or 

 to close-fertilize. 



Obviously the flower behavior of these 

 two varieties affords opportunity for 

 abundant cross-poiiinations both ways be- 

 tween the two trees. In the forenoon 

 pollen may be carried from Panchoy to 

 Taylor and in the afternoon there is op- 

 portunity for pollen to be taken from 

 Taylor to Panchoy. But if either tree 

 stands entirely alone, with no other vari- 

 ety of avocado near or within insect range, 

 there is very little chance that there will 

 be pollination at the proper time. 



A further point of special significance is 

 that the growing of a solid block of trees 

 of any variety of avocado tends to isolate 

 the trees and to reduce the chances for 

 proper pollination. The avocado is propa- 

 gated vegetatively by budding or graft- 

 ing. Thus all the many plants of any one 

 variety are, in reality, merely branches of 

 one original seedling plant. They all have 

 the same flower behavior. When planted 

 in solid blocks they all pass through the 

 same daily sequence in the opening of 

 flowers for the two periods. Their flow- 



