Hayes and Garber - Cucurbit Breeding

1910c). After becoming
CONTROLLING POLLINATION 69
familiar with the flower structure it
is important to determine at what time of day the pollen is
most easily collected and for what length of time the stigma is
receptive. Environmental conditions modify the expression
of these and other characters. However, some general rules
for different groups of crops may be given.
Certain tools are essential for the work of pollination. For
general work these are a small pair of thin, pointed scissors; a
pair of forceps with thin, pointed blades which meet exactly
and which are not too stiff; one or two dissecting needles; a
hand lens; a pencil; and small string tags for recording purposes.
Other special apparatus is necessary for difficult crosses.
Crossing of Small Grains. The technic of small grain crossing
is comparatively simple. Some practice, however, is necessary
in order to gain proficiency and to obtain a fair percentage of
seeds set. In some of the earlier directions it was stated (Hays,
1901) that it was necessary to make crosses of wheat at about
4 o'clock in the morning. Leighty and Hutcheson (1919) have
determined the period in which blooming takes place at University
Farm, St. Paul, Minn., ,and at Arlington Farm, Rosslyn,
Va. The spikes were examined at 7 a.m., 12 n., and 5 or 6 p.m.
A flower was considered as having bloomed when the glumes
had opened appreciably. The period from 5 or 6 p.m., to 7
Of 2,977 wheat flowers on
or 8 a.m. was referred to as night.
69 spikes, 1,492 bloomed at night and 1,485 bloomed during the
day. About half of those which bloomed during the day bloomed
before noon. These figures are given to correct the erroneous
idea that it is always necessary to pollinate wheat early in the
morning. Environmental conditions may be an important
factor, for Salmon (1914), working in South Dakota, stated
that blooming was practically completed before 7 o'clock in the
morning.
Leighty and Hutcheson (1919) show that in wheat it is unsafe
to leave the spikes uncovered after emasculation. Seeds were
formed by 507 of 1,240 emasculated, unprotected
flowers at
University Farm, Minn, and 1,103 seeds were formed in 1,324
flowers similarly handled at Arlington Farm, Va. while less than 1
per cent, of flowers emasculated and covered with paper bags set
seed. Frear (1915) , working with Turkey winter wheat, obtained
80 per cent, seeds set on emasculated, uncovered spikes and less
than 1 per cent, on emasculated covered spikes.