go6 
Journal 0 } Agricultural Research 
Vol. XXIII, No. XX 
the optimal is 11 to 12 hours. The Tokyo seems to be better able to 
resist the advance of senescence than the other varieties. The Peking 
is particularly responsive to a definite light exposure in this respect 
and under the 13-hour day began shedding its leaves early in August. 
Table VIII .—Behavior of different varieties of soybeans planted May jz to June I and 
grown under daily light exposures of different lengths. 
Average height of plants on 
Aug. 5. 
Time of first blossoming. 
Treatment. 
Man¬ 
darin. 
Pe¬ 
king. 
To¬ 
kyo. 
Bi¬ 
loxi. 
Otoo- 
tan. 
Man¬ 
darin. 
Peking. 
Tokyo. 
Biloxi. 
Otootan. 
io-hour day, 5.30 a. m. 
In. 
In. 
In. 
In. 
In. 
to 3.30 p. m........ 
x8 
*3 
15 
x8 
23 
June 27 
June 25 
June 27 
June 30 
July x 
xx-hour day, 5.30 a. m. 
to 4.30 p. m. 
20 
14 
20 
20 
25 
...do_ 
...do.... 
...do_ 
...do_ 
Do. 
12-hour day, 5.30 a. m. 
to 5.30 p. m. 
20 
x6K 
20 
2X 
30 
...do_ 
...do_ 
...do. ... 
July 2 
July 4 
13-hour day, 5.30 a. m. 
to 6.30 p. m. 
27 
J 9 
27 
28 
36 
...do.... 
.. .do.... 
June 30 
July 5 
July 6 
Controls, full summer 
day length. 
25 
*7 
5 * 
31 
33 
July 2 
July 18 
Aug. 8 
Sept. 7 
xo-hour day, 5.30 a. m. 
to 3.30 p. m., under 
heavy shade. 
18 
XX 
15 
l8 
33 
June 28 
June 27 
June 28 
June 30 
July 2 
Appearance of plants Sept. 8. 
Treatment. 
Mandarin. 
Peking. 
Tokyo. 
Biloxi. 
Otootan. 
xo-hour day, 5.30 a. m. to 3.30 
p. m. 
Leaves green 
Leaves green 
Leaves green 
Leaves yel¬ 
lowing. 
Leaves yel¬ 
lowing. 
xx-hour day, 5.30 a, m. to 4.30 
p. m. 
Leaves yel¬ 
lowing. 
Most leaves 
green. 
.do. 
Mostly leaf¬ 
less. 
Leafless. 
12-hour day, 5.30 a. m. to 5.30 
p. m. 
Few green 
leaves. 
...do. 
Few green 
leaves. 
Few green 
leaves. 
13-hour day, 5.30 a. m. to 6.30 
P. m. 
Leafless. 
Stalks dead, 
leafless. 
.do. 
Most leaves 
green. 
Leaves green. 
Controls, full summer day length. 
Nearly leaf- 
, less. 
Leaves green 
Green, still 
flowering. 
Still grow¬ 
ing. 
Still grow¬ 
ing. 
xo-hour day, 5.30 a. m. to 3.30 
p. m., under heavy shade. 
Mostly leaf¬ 
less. 
.. .do. 
Leaves green 
Few green 
leaves. 
Leafless. 
Considering that a light period which is unfavorable for vegetative 
activity may cause death or dormancy, as the case may be, the question 
arises as to the relation of the light period to emergence from dormancy. 
The line of division between death and dormancy is often a very narrow 
one, and there are varying degrees or conditions of dormancy. It appears 
that the time and conditions of emergence, or whether it shall occur at all, 
may depend in part upon the length of day under which the plant enters 
upon the state of dormancy. The behavior of the Kudzu vine (Pueraria 
hirsutus (Thunb.) Scheid.) in this particular is of interest. Beginning 
May 12, seedlings which had been growing since January 5 were given a 
io-hour day through the summer while control plants were exposed to 
the full day length. Under the io-hour day growth of the aerial portions 
of the plant soon ceased and the foliage assumed a very dark green color. 
The basal portion of the stem became considerably enlarged. The controls 
grew vigorously through the summer. Both lots of plants were transferred 
to the greenhouse September 15. In both cases the leaves gradually 
withered and fell and the plants became dormant, although this condition 
was not fully readied till early in December. By January 11 new shoots 
