Hayes and Garber - Cucurbit Breeding

164 BREEDING CROP PLANTS
"4. When a sufficient number of F 2 individuals are available, the
grandparental types should be recovered.
"5. In certain cases individuals should be produced in F 2 that show a
more extreme deviation than is found in the frequency distribution of
either grandparent.
"6. Individuals from various points on the frequency curve of an F 2
population should give F 3
populations differing markedly in their modes
and means.
FIG. 36. A, N. alata fjrandiflora; B, Fi of N. langsdorfii X N. alata grandif.ora;
C, N. langsdorfii (1911); D and E, extremes of the Fz generation (1912) X
%. (After East.)
"7. Individuals either from the same or from different points on the
frequency curve of an F 2 population should give Fz populations of diverse
variabilities extending from that of the original parents to that of the
Fz generation.
"8. In generations succeeding the F 2 ,
the variability of any family
may be less but never greater than the variability of the population
from which it came."
All of the above eight conditions have been obtained in experiments
and no fact directly opposed to them has been discovered.
The quantitative characters in tobacco which have been
studied are, therefore, typically Mendelian in their inheritance.