334 
Journal of Agricultural Research 
Vol. XXIX, No. 7 
In a cross between Sonora and Tur¬ 
key wheats, Bryan and Pressley ( 8) 
found the Fi progeny almost exactly 
intermediate between the parents in 
time of first heading. In the F 2 genera¬ 
tion the range of variation was but 
slightly greater than that of both par¬ 
ents but inclined toward the late par¬ 
ent. In the F 3 progeny several early 
plants were isolated which were almost 
as early as the early parent. In the F 4 
progeny, the range of heading dates of 
a somewhat larger number of early 
plants was considerably narrower than 
that of the early parent. 
EXPERIMENTS WITH OTHER CROPS 
In studies of earliness in peas, Men¬ 
del (I, p. 337), found that the time of 
flowering of the Fi generation was in¬ 
termediate between those of the par¬ 
ents. Keeble and Pellew (11), in their 
work with time of flowering and stature 
of peas, concluded that lateness was 
dominant over earliness and that ap¬ 
parently there is a relation between the 
morphological and vegetative charac¬ 
ters and the period of flowering in 
plants. 
Leake (12), in studying the blooming 
time of cotton, found the Fi generation 
intermediate, while the F 2 progeny 
formed a regular curve with the mean 
nearest the late parent. 
Emerson and East (5) found that the 
time of first exposure of the anthers was 
distinctly intermediate in the Fi gen¬ 
eration of a cross between a dent corn 
(late) X pop corn (early). In the F 2 
progeny some of the plants were nearly 
as early as the earliest of the early 
parent and others as late as the late 
parent. Ten families held the same 
relative order of ripening as of flower¬ 
ing, while the parent varieties were fur¬ 
ther apart in ripening than in blossom¬ 
ing. 
Hoshino (10), working with rice, 
found that emergence of the head in the 
Fi generation inclined to that of the early 
parent. In the F 2 progeny he found 
two segregation groups, with the mini¬ 
mum frequency midway between the 
variation ranges of the parents, and 
with the early group the larger. Fur¬ 
ther segregation groups appeared in the 
F 3 and F 4 generations. He explains his 
results by a 3-factor hypothesis. 
Caporn (4), in reporting on the in¬ 
heritance of earliness in an oat cross, 
found the Fi progeny intermediate be¬ 
tween the parents in ripening. In the 
F 2 progeny much variation was ob¬ 
served, but in the F 3 generation the 
variation did not extend so far as that 
of the parents. 
INDICES OF EARLINESS IN CEREAL CROPS 
The indices used in the studies on the 
inheritance of earliness in the cereal 
crops have varied considerably. Far- 
rer (6) took as his index the change in 
color of the peduncle immediately be¬ 
low the spike. Biffen (2) used the fully 
ripe condition, as indicated by yellow 
straw and glumes and hard grain, al¬ 
though in order to get a comparable 
reading of his populations he also used 
half ripe, as indicated by yellow awns, 
other parts yellowish green, and the 
grain soft. His third class was green 
throughout. Thompson (15) used the 
term “fully ripe” for the time when 
the central kernels of the spike reach 
the dough stage. Caporn (4) in studies 
on oats considered fully ripe to indicate 
disappearance of the last trace of green¬ 
ness from the tips of the paleae. 
Freeman (7) used as the index of 
earliness in wheat the date of appear¬ 
ance of the first head on each plant, as 
did also Bryan and Pressley (3 ). 
Hoshino (10), in rice, used the shooting 
time, i. e., the appearance of the first 
spikelet above the sheath of the inflo¬ 
rescence. Emerson and East (5) used 
the time of first exposure of the anthers 
in corn. 
In comparing earliness of varieties of 
cereals in agronomic experiments, the 
progression of the variety toward ma¬ 
turity usually is designated by several 
different stages. In wheat these gen¬ 
erally include first heading, fully headed,, 
first ripe, and fully ripe. There is 
usually quite close correlation between 
these different stages in the develop¬ 
ment of the plants. Then, in all but 
the exceptional cases, the stage that 
will be most sensitive, that is, that will 
show the greatest divergence in time of 
appearance, should most accurately 
show the relative earliness of varieties or 
strains. It is well known, and also has 
been the writer’s experience in agro¬ 
nomic note-taking for a number of years, 
that the relative difference in earliness 
at first heading is considerably greater 
than at maturity. The rate of develop¬ 
ment of the wheat plant is more rapid 
at the time of ripening than at the time 
of heading. Ripening often is more or 
less abnormal also, owing to the effect 
of high temperatures, drought, etc. 
Harlan (9, p. 8, 9), found in his 
studies on barley that the evidence 
seemed all in favor of the first emerg¬ 
ence of the awn as a character pos¬ 
sessing heritability equal to that of 
most plant characters. He also states 
that the date of ripening is subject 
to influences induced by climatic 
factors. In awned varieties of wheat 
