K.— BOTANY. 205 



All the flowers that may be open at any one time, on trees of the same 

 clonal variety, are in either the female or the male condition. If the trees 

 belong to one of the varieties placed in ' Class A ' by Stout, of which the 

 Taylor variety is taken as an example, the flowers when they first open 

 in the morning are found to be functioning as females with a receptive 

 stigma, but the anthers are not yet mature. 



About midday these female flowers close, for none but flowers in the 

 female state are open on the trees, and another set of flowers then opens 

 in the early afternoon, normally without any overlapping, so that there 

 are never on any tree of ' Class A ' flowers in th^ male and flowers in the 

 female condition open at one and the same time. These afternoon flowers 

 are found to be in the male condition with the stigma withered ; the 

 anthers are in an upright position, with their valves open and shedding 

 their pollen. 



Careful investigation of trees of ' Class A ' has shown that the flowers, 

 when they first open, function as females for some four hours in the 

 forenoon ; they then close about midday, remain closed all night and all 

 the following morning, and reopen on the afternoon of the second day in 

 the male condition. Self-pollination of individual flowers is thus rendered 

 impossible by this sex-alternation, and since there is normally a definite 

 time interval, about midday, when no flowers on trees of the same ' Class ' 

 are open, cross-pollination on the same tree or between different trees of 

 the same clonal variety can rarely occur. 



This rhythmic phenomenon is all the more remarkable because there 

 is an entire reversal of the process just described in other clonal varieties 

 and individual seedlings, which Stout places in his ' Class B.' 



In trees belonging to ' Class B ' the flowers are in the male condition 

 when those of ' Class A ' have their stigmas receptive, and sltb female when 

 the pollen of ' Class A ' trees is being shed. These reciprocating changes 

 in sex thus provide the opportunity for mutual cross-pollination between 

 the trees of ' Class A ' and those of ' Class B.' 



The practical application of this discovery hardly needs pointing 

 out, but it is clear that an orchard planted with trees of only one variety 

 is not likely to yield a rich harvest of fruit ! That the right selection 

 of the varieties for interplanting can now be made, the grower has to 

 thank the botanist, since it is now possible for him to obtain a maximum 

 yield of fruit from his plantation. 



I was interested to learn recently from a former Director of Agriculture, 

 Bermuda, that they could never get Avocados to fruit in the Bermudas. 

 Prizes were ofiered and cultivation devices, spraying, &c., were tried, all 

 to no purpose. Evidently they were growing trees of only one clonal 

 variety, and had they known of the sex-alternation they would have been 

 able at an earlier stage to develop a profitable industry. 



The scientific research which has revealed and elucidated the natural 

 phenomenon exhibited by the Avocado, the full significance of which is 

 a matter of so much conseqixence in the practice of husbandry, is an 

 interesting example of hidden possibilities being brought to light by 

 scientific research ; and suggests comparison with some of the economic 

 problems in the botanical direction, where a demand is made on the 

 scientific worker to produce some economic plant, of a type suited to the 



