Oct. 1, 1924 
Inheritance of Earliness in Wheat 
335 
or barley the first appearance of the 
awn is a more definite stage than the 
first appearance of the spike. In 
awnless varieties emergence of the 
tip of the spike is practically as 
definite as the first appearance of the 
awn in an awned variety. 
AGRONOMIC NOTES ON EARLINESS 
IN WHEAT 
In the studies herein reported, 
curves have been prepared from the 
data on heading and ripening of 
varieties of wheat in the wheat classifi¬ 
cation nursery at Davis, Calif., in 
the year 1922, and also from Chico, 
those included within the last six 
inches at each end of the row. Fre¬ 
quently the plants in this location 
would develop nearly as rapidly as 
those in the remainder of the row, 
while at other times their growth may 
be definitely retarded. 
The curves show a comparatively 
wider divergence of the dates of first 
heading and all headed than of the 
dates when the first heads ripened and 
when all were ripe. The difference, 
for example, in the date of first heading 
of Marquis and of Sunset was 25 days; 
in date of first ripening it was 17 days; 
and in date when all were headed it was 
15 days. Figure 1 shows that most of 
AZ4Y- Ut/A/E 
Fig. 1.—Curves showing dates of first heading, all headed, first ripening, and all ripe, for 29 representa¬ 
tive varieties of wheat grown in the wheat classification nursery at the University Farm, Davis, Calif., 
in 1922 
Calif., in 1920, for comparison. Both 
seasons were normal, except at Chico 
where the temperature was relatively 
high during the period of ripening. 
Figure 1 shows the curves of first 
heading, all headed, first ripe, and all 
ripe for 29 representative varieties for 
the Davis nursery in 1922. 
All varieties in the classification 
nursery are pure lines, and the date of 
first heading has been fixed * as the 
time when the tips of the first 3 or 4 
heads appear in the pure-line row. 
The date recorded for the stage of 
development termed “ all-headed” is 
the time when all heads not influenced 
by border position were fully exerted. 
The plants favored by position were 
the varieties present a relatively similar 
divergence. Little Club, when com¬ 
pared with Arcadian, is an exception in 
that it heads earlier but ripens later 
than Arcadian. Farrer ( 6 ) also made 
the observation that the variety of 
wheat that heads first is by no means 
the first to ripen. It may be noted 
that this behavior is exceptional. 
Club varieties are abnormal in their 
behavior since they require a longer 
fruiting period than the common 
wheats. 
Figure 2 gives heading and ripening 
data for the same 29 varieties grown at 
Chico, Calif., in 1920. In this season 
the difference in time of first heading of 
Sunset and Marquis was 28 days; in 
