May 12, 192J 
Resistance to Stem Rust in a Cross of Common Wheat 459 
The nature of the processes involved in bringing about the heading 
period has been a matter of speculation for some time. The climatic 
units which control these processes and permit winter grains to produce 
seed are finely interwoven. Although temperature and moisture are 
very important factors in the growth and maturing of plants, it is quite 
evident from the plant life about us that the time of flowering and 
fruiting of most plants is definitely connected in some way with the 
advance of the season. Gamer and Allard (6) have clearly demonstrated 
this third factor to* be the change in length of day and night. They 
found that certain plants which ordinarily require a short day for flowering 
and fruiting could be induced to flower and fruit in the middle of the 
summer by shortening the length of day to that which was normal for 
the regular flowering season. This was done by placing the plants in a 
dark-house for a certain number of hours each day. 
In contrast to this group of plants which require a short day for flower¬ 
ing and fruiting, is that group of plants which require a long day of light. 
These plants flower regularly in the late spring or early summer. Gamer 
and Allard place our small grains in this group. 
As regards the inheritance of the growli-habit character, the results 
reported by previous workers do not appear at first to be in full agreement. 
Spillman {12) reported in 1909, that the winter character was dominant 
over the spring character in a cross between a winter common wheat and 
a spring club wheat. Fruwirth (4, p. 176) in 1910, cites Tschermak as 
having reported that the winter type was dominant over the spring type. 
When sown in the fall, the first generation of hybrids wintered over 
somewhat better than the tme winter forms; but when sown in the spring, 
they remained dormant through nearly the whole summer. Single 
shoots appeared and began to blossom, but they produced no seed. 
Gaines (5, p. 42-45) in 1917, reported that he obtained a segregation 
of spring and winter types from a cross between 2 spring varieties of 
barley, Rice and Beardless. The Fj when sown in the spring, headed 
normally. In the F2 there was a ratio of 3 winter plants to 13 spring 
plants. The plants in the third generation bred fairly close to expected 
ratios. He found that seasonal variations influenced the heading periods 
and consequently the ratios. The segregation in the Fj, however, 
indicates a dominance of the spring type over the winter type. 
A complete and detailed study of the genetic nature of growth habit 
in wheat varieties has been made recently by Vavilov and Kouznetzov 
{18). They crossed a common winter wheat with a club spring wheat 
and found a clear dominance of the spring character over the winter 
character. There was a complicated segregation in the Fg, and some of 
the segregates (including many intermediates) were homozygous in the 
Fg. Of the 552 Fg plants, 500 were early or late spring plants and 52 
were typical winter plants. The results obtained by the writer on the 
inheritance of spring and winter habit are quite in accord with those of 
Vavilov and Kouznetzov. 
MATERIALS AND EXPERIMENTAL METHODS 
Marquis, a hard red spring common wheat of high quality, was crossed 
with Kanred in the summer of 1918. The latter, which is immune from 
several different biologic forms of stem rust, is a high yielding selection 
from Crimean hard red winter wheat. 
