560 Journal of Agricultural Research voi. xvm, no. u 



as used in this paper refers to the duration of the illumination period for 

 each 24-hour interval. 



As a part of the present investigation a series of plantings of soybeans 

 was made in the field at intervals of approximately three days throughout 

 the season, in order that the effects produced by different dates of plant- 

 ing might be compared with those produced by artificially shortening 

 the length of the daily exposure to light. 



BEHAVIOR OF THE PLANTS TESTED 



The initial experiment Avas made in the summer of 191 8, and in this 

 instance a box containing the Peking variety of soybeans in blossom 

 and three pots containing Mammoth tobacco plants which had been 

 growing for several weeks were first placed in the dark chamber at 4 

 p. m. on July 10 and removed therefrom at 9 a. m. the following morning. 

 This treatment was continued each day till the seeds of the beans and 

 tobacco were mature. All subsequent experiments were made during 

 the year 191 9. Details of the tests for both years follow. 



SOYBEANS (SOJA MAX (l.) PIPER) 



(a) Mandarin * (F. S. P. I. No. 36,653), early maturing: 



(i) Exposed to light from 10 a. m. to 3 p. m. Planted May 8, up May 

 17, and placed in dark house May 20. First blossoms appeared June 12 

 on test plants and June 15 on controls. Average height of test plants 

 6 to 7 inches and that of controls 18 to 20 inches. After blossoming, the 

 growth and development of the seed pods was much more rapid in the 

 test plants than in the controls. 



(2) Exposed to light from 9 a. m. to 4 p. m. Planted May 8, up May 

 17, and placed in dark house May 20. First blossoms appeared June 10 

 on test plants and June 15 on controls. Average height of test plants 

 9 to 10 inches and that of controls 19 to 20 inches. 



(3) Exposed to light from 6 a. m. to 6 p. m. Planted and placed in 

 dark house June 11, up June 16. First blossoms appeared July 7 on 

 test plants and July 14 on controls. Average height of test plants 14 

 to 15 inches and that of controls 32 to 33 inches. Six weeks after blos- 

 soming the seed pods and foliage were still green and the plants stocky, 

 whereas, under the same conditions, the Peking variety, listed below, 

 showed many brown, mature pods, foliage yellowing, and the plants 

 slender. 



(b) Peking ^ (F. S. P. I. No. 32,907), medium maturing: 



(i) Exposed to light from 10 a. m. to 3 p. m. Planted May 8, up May 

 17, and placed in dark house May 20. First blossoms appeared June 

 12 on test plants and July 21 on controls. Seed pods on test plants 



I Horticultural variety. 



