Hayes and Garber - Cucurbit Breeding

74 BREEDING CROP PLANTS
flowers which had just opened, no pollen remained. Small
pieces of blotting paper were used to remove excess moisture and
then pollen was applied. Fifteen flowers of lettuce were first
crossed by this means and some seed was produced in each
flower. The lettuce flowers and those of other closely related
Compositse close soon after pollination.
Certain small rubber-bulb syringes have been found satisfactory
for field work. These are used to depollinate the flowers
with water. For a complete description of artificial crosspollination
of alfalfa flowers the reader is referred to Oliver. In
the flower to be used as the female, the anthers have already
dehisced but can not perform the act of fertilization until the
flower is tripped. To trip the flower and secure as small a percentage
of pollination as possible
tripping and depollinating as well as the technic of crossing is a
matter of practice. Oliver records that more than two-thirds of
the alfalfa pollinations were successful by this method.
is the aim. The technic of
Summary of Technic of Crossing. Some important features
of the technic of crossing may be summarized.
1. Make a careful study of the structure of the flower before
commencing operations. This may be done with the aid of a
dissecting microscope.
2. Determine which flowers produce the larger, healthier seeds
and which set seeds the more freely.
3. Learn the normal method of blooming of the flower, the
period of receptivity of the pistil, and the length
of time the
pollen grains are capable of functioning.
4. Procure the necessary tools and see that these are of an
efficient kind for the work to be undertaken.
5. Be careful not to injure the flowering parts any more
than is necessary. Do not remove the surrounding flower parts,
i.e., petals in flowering plants, glumes of grasses, etc. unless
necessary.
6. A few crosses well made are of much greater value than
many pollinations carelessly executed.