ptivity is longer than in the Japanese and hybrid chestnuts
tested. They maintained full receptivity on the 22nd day after the
beginning of anthesis.

It is commonly believed that bagging as well as emasculation may
seriously affect the yield from controlled pollination. This is not
always the case. One of the Japanese trees and one hybrid tree (S8 x J)
yielded fully as many nuts from controlled (under best conditions) as
from open pollination. On all other trees the effect of bagging was more
or less adverse.

The Effect of Emasculation on Nut Yield

Emasculation involves the removal of the unisexual male catkins and the
male part of the bisexual catkins. In the course of the controlled
pollination work it has often been found that the female flowers drop
off in the bag before the burs start to develop. This has especially
been encountered in Japanese x American hybrids and back-crosses. It was
thought that this perhaps was due to injuries resulting from
emasculation. The following small experiment was carried out in order to
determine if this was actually true.

A Japanese x American and a Japanese x (Japanese x American) hybrid were
used as the female parents. On these trees some flowering branches were
bagged which had been emasculated normally, on other branches only the
unisexual catkins were removed, while the bisexual catkins were left
intact. Some branches were bagged without any emasculation, and some
flowering branches were just tagged. The number of female flowers was
counted in all cases. Pollinations were performed 3 times, that is, were
repeated on the third and fifth day after the first pollination. This is
the procedure ordinarily used for our controlled pollinations. Chinese
pollen was used on both trees. Nut set expressed as per cent of the
number of pollinated flowers, times three, (because ordinarily there are
3 nuts in every bur) was taken as a measure of how successful the
pollinations had been. The results are shown in Table 2.

Table II. The Effect of Emasculation on Nut Yield

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Type of Treatment No. of [Symbol: female]'s at Nut set as
time of first expressed in %
pollination of [Symbol: female]'s
at time