236 
Journal of Agricultural Research 
Vol. XXVII, No. S 
blooming might be considerably more abundant than it was in this 
experiment under certain environmental conditions. 
The effect on blooming of the duration of the daily illumination period, 
or of changes in the duration of this period, was not determined. It is 
known from other studies, however, that many varieties of wheat will 
bloom and mature in less time after planting when subjected to a long 
daily illumination period as compared with a shorter period. 
According to Godron (j) wheat flowers open at 4.30 a. m. when the 
temperature is at least 16 0 C., with blooming ending at 6.30 to 7 o’clock. 
Rimpau ( 11) states that under favorable conditions blooming begins 
at 4.30 a. m. and occurs during various periods of the day. He reports 
that he observed open flowers after 6.45 p. m., but does not mention the 
latest hour at which blooming was observed. Koernicke (7) states that 
open flowers may be observed at all hours of the day, the earliest around 
5.45 a. m., the latest at 8.30 p. m. Friiwirth (2) observed flowers bloom¬ 
ing during the day from 4.30 a. m. to 7 p. m. under favorable conditions. 
Obermayer (9) found that blooming began even before 5 a. m. and con¬ 
tinued throughout the day, with a small number blooming after 7 p. m. 
Salmon (xa), describing conditions in western South Dakota, says: 
“It is exceptional to find wheat in bloom after 7 a. m. under normal 
conditions.” 
ORDER OE BLOOMING 
Table IV shows the positions on the head of the first five flowers bloom¬ 
ing on each of the seven heads studied. On five of the seven heads the 
first flower bloomed in the lower half of the uppermost third of the head; 
on one head, in the upper half of the middle third; and on another head, 
in the upper half of the uppermost third. 
Fruwirth (2) states that the first blooming occurs between the middle 
of the head and the top of the middle third. Percival (jo, p. 122-129) 
says that the position of the first flower to bloom is generally in the middle 
third of the head, usually in the upper part. Godron (3) found that the 
first flower bloomed below the upper third of the head. Rimpau (11) 
states that the first flower began to bloom at a point two-thirds to three- 
fourths of the distance from the base of the head. 
Table V shows the position of the last flower observed to bloom on 
each head. On heads not included in this study flowers in the terminal 
spikelet have occasionally been seen blooming before those in spikelets 
located in the upper third of the head. 
Table IV .—Number of spikelets in each of seven wheat heads and position of the 
spikelets, numbered in order from the base of the spike, in which were located the first 
five and the last blooming flowers, with flower number of last flower 
Head No. 
Total 
number 
of spike¬ 
lets. 
Position number of spikelets where occurred 
blooming of first five and last flowers. 
Num¬ 
ber of 
last 
flower. 
zst. 
1 2d. 
3d. 
4 th. 
5 th. 
Last. 
2 D. 
20 
16 
14 
IS 
20 
17 
5 
4 
3 c. 
18 
13 
15 
14 
12 
II 
3 
3 
4 A . 
22 
20 
22 
IO 
21 
9 
3 
4 
S C. 
18 
12 
15 
13 
II 
14 
9 
3 
6 C . 
19 
l 6 
14 
II 
12 
13 
4 
3 
70 . 
21 
15 
17 
14 
13 
16 
8 
3 
8 B. 
23 
15 
12 
II 
13 
9 
2 
2 
