Hayes and Garber - Cucurbit Breeding

224 BREEDING CROP PLANTS
1. The heterozygous condition of most varieties.
2. The difficulties of obtaining crossed seed.
The heterozygous condition need not be further emphasized.
Conditions are much the same as in the fruit crops.
The Difficulties of Obtaining Crossed Seed. The technic
of making a cross is very simple. According to East (1908a),
"The flowers close slightly about dusk and open in the morning
between five and six o'clock. The pollen appears to be in the best
condition for use on the second day of blooming." Stuart (1915)
collects flowers to be used as the male parent in small sacks.
After the pistil is removed from these flowers the anthers are
tapped sharply with a pair of forceps, the pollen is collected
FIG. 54. Emasculated and unemasculated potato blossoms. (After Stuart.)
on the thumb nail and then applied to the pistil of the emasculated
flower. The flowers are receptive two to four days after
emasculation. East (
1908a) stated the belief that the potato is
usually self-fertilized. He also observed the fact that insects were
seldom seen to visit the flower. Salaman (1910-11) believes
it unnecessary to cover the flower before or after pollination.
Stuart, however, used 1-lb. bags and found that if a certain
amount of foliage was included in the bag the use of bags did
not cause a lowering of the number of seeds set. An average of
between one and two hundred seeds was obtained from each successful
cross by Stuart.
The chief difficulty is that many varieties do not bloom very