588 Wester: POLLINATION EXPERIMENTS WITH ANONAS 
half of May and continues throughout the summer and fall. 
Curiously enough, the flowers, which occur in great abundance, 
do not set until October and November, the fruit maturing in 
the spring. The pollination experiments with this species were 
started in May and continued during the following months. 
As already stated on a previous page, nearly all the pollinated 
flowers set, but with exceedingly few exceptions remained station- 
ary in size, 6-8 mm. in diameter, until November, when they 
started to develop and matured in the usual season. The few 
fruits whose development began immediately after the pollination 
of the flowers matured in December. 
The investigations indicate that the flowers of the cherimoya, 
the sugar apple, the custard apple, and the pond apple are pro- 
terogynous and entomophilous, though the pollinating agent of 
the last-named species has not been detected. 
Since the investigations here related began, the cherimoya, 
after the trees have grown larger, has without artificial pollination, 
though sparingly, set fruit in Florida less than 20 feet above tide 
water. In California and Southern France it likewise fruits at a 
low altitude. In some parts of the world, i. e., Hawaii, the species 
fruits only at an elevation of many hundred feet above the sea 
level. On investigation it may be found that this is due to the 
presence there of certain insects that do not occur at lower al- 
titudes. 
_ The sterility of the cherimoya in Florida has undoubtedly 
been due to the scarcity of blooms, which on this species is only 
one third of the number on the sugar apple, and to an insufficient 
number of insects to assist in the pollination of the flowers. As 
the trees grow larger and carry a greater number of flowers they 
may be expected to fruit more abundantly. 
It has been demonstrated that the sugar apple hybridizes 
readily with the cherimoya, custard apple, and pond apple; the 
cherimoya has also been successfully crossed with the pond apple. 
So far, the attempts to cross the soursop, Anona muricata L., with 
the cherimoya, sugar apple, and custard apple have failed. 
The extraordinary productivity of a few individual trees 
suggests a change in regard to the pollination of the flowers of 
these trees, possibly due to synacmy and self-pollination. Should 
