Journal of Agricultural Research 
Vol. XXVII, No. 3 
138 
The preceding experiment was repeated with two rows of Biloxi soy 
beans planted in the field which had germinated May 19 and 21, re¬ 
spectively. Beginning July 24, a portion of the plants were allowed to 
receive only 10 hours of light daily, this being accomplished by placing 
over the plants a ventilated, light-proof box which could be opened and 
closed as desired. In this case the exposure to the shortened day length 
was not begun until just as the plants were passing over into the flowering 
condition as a result of the natural decrease in length of day. Flower 
buds could first be seen on August 10 under the io-hour day and on 
August 22 under the natural length of day. The transition from the 
vegetative to the reproductive stage occurred considerably earlier than 
in the preceding experiment because the plants had been seeded much 
earlier. The results of the observations, presented in Table VI, are 
even more sharply defined than those of the preceding test with respect 
to the initial decrease in acidity, and bring out clearly the same general 
relationships as to the course of changes in acidity. This test empha¬ 
sizes the fact that under the conditions important changes in acidity as 
a result of abrupt shortening of the day length do not occur till after 
the lapse of 2 or 3 days. 
Table VI. —Showing the Ph value of the cell sap of the young, topmost leaves of Biloxi 
soy beans growing in the field when exposed to the natural change in length of day in 
summer, and when the daily light period was abruptly changed from the natural daylight 
period of summer to a io-hour period of illumination 
Date of sample. 
July 22. 
July 25. 
July 27. 
July 29. 
Aug. 1. 
Aug. 4. 
Aug. 7. 
Aug. 10 
Aug. 14 
Aug. 17. 
Aug. 22 
Aug. 25 
Aug. 30. 
Sept. 8. 
Plants exposed to natural 
change in length of day 
throughout the test. 
Plants exposed to natural 
change in length of day 
till July 24 and thereafter 
exposed to a io-hour day. 
Hour of 
sampling. 
1 
Ph value. 
Hour of 
sampling. 
Ph value. 
a, m. 
9 - 50 
9. 00 
6-37 
6. 38 
a. m. 
IO. 20 
6-37 
9 * 15 
6. 80 
IO. 25 
A 57 
8. 50 
6. 27 
IO. 30 
6-39 
9 - IS 
6. 11 
10. 30 
6.28 
io -35 
6. 20 
9 - °5 
6. 20 
9-25 
6. 07 
10. 45 
6. 01 
10. 30 
6. 20 
9. 10 
6. 03 
9-35 
6. 18 
11. 00 
6. 16 
10. 15 
6. 04 
9. 00 
6. 08 
10. 00 
9 - 45 
9 - 5 o 
9 - 45 
1 
6. 24 
6. 07 
6. 10 
6. 06 
Studies were made on acidity relations in the developing seed pods 
of Peking soy beans, which had germinated June 27, as representing the 
final features of reproductive activity. In the earlier stages of develop¬ 
ment the seed pods in their entirety were necessarily taken, but as soon 
as the seeds had attained sufficient size these were separated from the 
hulls. The samples were collected at 1.30 to 2.30 p. m. For analysis 
the seeds in the more mature stages were ground with distilled water. 
The results are shown in Table VII. The hulls, constituting the vege¬ 
tative portion of the fruit, increase in acidity as they develop, while the 
