Hayes and Garber - Cucurbit Breeding

46 BREEDING CROP PLANTS
order to illustrate the general results. The theoretical explanation
is given, as an appreciation of these phenomena is essential
in obtaining a correct plant breeding perspective.
The most extensive studies made have been those with maize.
As this crop is almost entirely cross-pollinated under natural
field conditions it is an admirable one to contrast with selffertilized
plants. Table VIII presents differences in yield and
height obtained at the Connecticut Station with four self-fertilized
strains of Learning Dent. These strains were grown only
in small plots, therefore differences are only indicative of the
general results which may be expected. Crosses between individual
plants within a strain that had been selfed six or seven
years, were not appreciably more vigorous than the progeny of
self-fertilized seed. These strains also differ in other characters,
such as shape of ear, width of leaf, and color in various organs.
One strain of Learning Dent No. 1-12 was self-fertilized for about
seven years. It produced well-developed tassels but few ears
and was eventually lost.
TABLE VIII.
THE EFFECT OF INBREEDING ON THE YIELD AND HEIGHT OF
MAIZE