Hayes and Garber - Cucurbit Breeding

94 BREEDING CROP PLANTS
grains on heterozygous F? plants and that of hulled grains on
heterozygous F s plants. Some heterozygous F 2 plants with low
percentages of hulled grains gave heterozygous progeny with correspondingly
low percentages. A similar behavior was obtained
in the progeny of heterozygous plants with high percentages of
hulled grains, while plants with intermediate percentages of
hulled grains gave heterozygous progeny with low, intermediate,
and high percentages in different plants. This suggests the
presence of a factor which affects the percentage of hulled and
hull-less grains of heterozygous plants.
Pubescence. Cultivated varieties of oats differ in the amount
and in the presence and absence of basal hairs on each side of the
callus. In some crosses only one factor is involved, in others two
factors.
In some crosses between parents which have different
degrees of pubescence there is an increase in the number of basal
hairs, and forms are obtained in F 2 which have more pubescence
than either parent, likewise forms which lack pubescence. Certain
wild forms of Avena fatua carry two independently inherited
factors for pubescence (see Surface, 1916; Zinn and Surface,
1917; Nilsson-Ehle, 1908; Love and Craig, 1918c).
Characters of Base of Lower Grain. In wild forms of A vena
fatua and cultivated forms of Avena sterilis there is a distinct
articulation at the base of the lower grain. According to Surface
(1916) this causes wild oats to shatter while in cultivated races of
saliva the grains are not easily separated from their base and do
riot ordinarily shatter. The FI generation of a cross between
A .
fatua and Kherson was intermediate as regards the base of the
lower grain, but nearer the cultivated form, while the upper grain
had a base similar to the cultivated parent. Segregation in F z