ceptive and how long they remain in this condition. Two
Chinese, two Japanese and two hybrid chestnuts of the combination (Jap.
x C. pumila) x Jap., the so-called S8xJ, were used as the females in the
study. Emasculation and bagging was done at the beginning of anthesis,
that is, when the first unisexual male catkins began to shed pollen.
Three different pollen sources were used on each female parent; they
were of the same species or hybrid combination as the female. The
following diagram shows the pollination schedule used.

Pollen source Time of pollination in days
No. after beginning of anthesis
5 9 13 17 22
-----------------------------------------------
1 X X X
2 X X X
3 X X X

For example, the Chinese female trees were pollinated with pollen from
three other Chinese trees (in the diagram "Pollen source No. 1, 2 and
3), which open their anthers on successively later dates. This
pollination schedule was used to avoid prolonged storing of the pollen.

[Illustration: Fig. 2. Showing, above, _C. mollissima_, Chinese
chestnut, left, and _C. seguini_, seguin chestnut, right, parents of
_mollissima_ x _seguini_ hybrid below. Note clustered burs in
hybrid--more than twice the number appearing in the _mollissima_ parent.
Leaves and habit of tree resemble more the _mollissima_ parent. About
1/6 natural size. Photo by B. W. McFarland, Conn. Agric. Expt. Sta.,
Sept. 25, 1953.]

To carry on pollination the bags are removed and the pollen-bearing
catkins are brushed lightly over the stigmas several times, one or more
fresh catkins being used in each bag. These catkins are left in the bag.
The bags are then replaced and permanently removed when danger of
outcrossing is eliminated, in this case 10-14 days after the last
pollination.

The number of nuts collected at the time of harvesting compared with the
number of female flowers pollinated was taken as a measure of how
successful the pollinations were.

The results showed that five days after the commencement of anthesis a
high proportion of the female flowers is receptive. The Japanese and
hybrid trees have a definite peak of the period of receptivity between 9
and 17 days after anthesis begins; thereafter, receptivity drops off
sharply. The data from the Chinese trees indicated that the period of
maximum rece