336 
Journal of Agricultural Research 
Vol. XXIX, No. 7 
date of first ripening, 16 days; and in 
date when all were ripe, 13 days. In 
general, the Chico data agree very 
closely with the Davis data, except that 
the high temperatures reduced the 
length of the ripening period. 
EXPERIMENTAL PROCEDURE AND 
DATA 
The index of earliness used in the 
studies reported in this paper was the 
date of emergence of the tip of the 
first spike. This is believed to be 
the most dependable index for study¬ 
ing earliness in cereals under California 
conditions. 
PARENT VARIETIES 
The cross used in this study was 
between a pure line of Marquis and a 
pure line of Sunset, the latter being the 
earliest of the Australian varieties of 
wheat introduced thus far. In a col¬ 
lection of over 1,400 foreign and do¬ 
mestic wheats, including a considerable 
number of early wheats from India, 
grown in 1920 at the United States 
Plant Introduction Station, Chico, 
Calif., Sunset was the first variety to 
head. Marquis is considered a moder¬ 
ately early variety throughout the 
northern spring-wheat belt of the 
United States and Canada, but when 
e/z, C/6///& 
/O 20 30 /0 20 c 90 3 /& 
Fkj. 2. 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 Plant Introduction Station, 
Chico, Calif., in 1920 ’ 
The date of first ripening was taken 
as the time when the tip spikelets of 
the 3 or 4 earliest heads in the row 
began to take on the natural color of 
maturity and their kernels began to 
show a definite stiffening or hardening. 
It may be added that the color of 
maturity of the chaff varies. In 
white-glumed varieties it is nearly 
white to white or yellowish. In 
brown-glumed varieties it is yellowish 
brown to brown. The date on which 
the plants were recorded as all ripe 
normally is the time when all heads 
in the row were fully ripe, except 
those subject to border effect, which 
were not considered. At this stage 
the kernels were hard and the color of 
the glumes had changed to normal at 
maturity. 
grown in California it is quite late in 
comparison with Sunset. 
Pj MATERIAL AND F x PROGENY 
The cross, Marquis X Sunset, and 
its reciprocal, was made in 1920 at 
Chico, Calif. In making the cross two 
spikes from each variety were used, and 
the pollen was obtained at random from 
each of the parent rows. Nine appar¬ 
ently crossed kernels were obtained 
from the cross Marquis X Sunset and 
21 kernels from the reciprocal Sunset X 
Marquis. 
The Fj generation was grown at 
Chico. The date of first ripening of 
this population as a group was noted 
to be slightly earlier than that of the 
Marquis parent. 
