Feb. a, 1924 
The Blooming of Wheat Flowers 
235 
blooming under most favorable conditions as 13 to 18 minutes, but states 
that it sometimes is completed in shorter periods, even as low as 2 or 3 
minutes, while under less favorable conditions and in the early morning 
it requires from 25 to 32 minutes. The average duration is 22 minutes. 
Percival (jo, p. 122-129) states that the time taken in opening and 
closing completely varied from 8 to 30 minutes or more, the average 
being 20 minutes, while Hays (4, p . 50) says, “The floret (of wheat) 
usually opens about dawn, and closes again within an hour. ” 
PERIOD OF BLOOMING 
Flowers were observed blooming during various hours of daylight and 
darkness. “Day” is hereafter referred to as a 24-hour period; “day¬ 
light,” the period from sunrise to sunset; “twilight,” the combined 
periods of approximately hours each before sunrise and after sunset. 
“Night” includes the remaining portion of a day not previously desig¬ 
nated. The division of the day into these periods was based on the 
time of sunrise and sunset (Table II) kindly supplied by the United 
States Naval Observatory at Washington, D. C. 
Of the 406 flowers observed, 6.9 per cent* bloomed at night; 6.9 per 
cent during twilight, and 86.2 per cent in the daylight. The total num¬ 
ber of flowers blooming on each head and the numbers blooming in each 
period of the day during the complete period of anthesis are shown in 
Table III. 
Table II .—Time of rising and setting of the sun at Washington, D. C., May 14 to 19,1921 
May 14. 
May 15. 
May 16. 
May 17. 
May 18. 
Sunrise, a. m. 
4-56 
7.12 
4-55 
7-13 
4-54 
7.14 
4-54 
7-15 
4-53 
7.16 
Sunset, p. ra. 
Table III .—Total number of flowers blooming and numbers blooming during stated 
periods of the day, during the complete period of anthesis , on each of 7 heads of wheat 
Number of flowers blooming. 
Head No. 
Total. 
In day¬ 
light. 
In twi¬ 
light. 
In night. 
2 D . 
59 
52 
75 
41 
5i 
53 
75 
52 
42 
62 
4 
1 
7 C. 
r 
4 
0 
6 
4 A. . . . . .. . 
T 
0 
4 
c c . 
37 
47 
47 
63 
zf 
I 
*T 
2 
6 C . 
2 
O 
2 
7 D . 
2 
2 
8 B ... 
O 
< 
O 
7 
Total . 
406 
100 
350 
86.2 
28 
28 
Per cent . 
6.0 
6.0 
y 
7 
The fact that most of the flowers under observation bloomed in day¬ 
light does not mean, necessarily, that light is essential for blooming. 
As shown elsewhere in this paper, wheat flowers kept in a dark room 
bloomed completely and in the same manner as flowers under natural 
conditions. Although no data are at hand, it is probable that night 
