Mar. 1, 1920 Effect of Length of Day on Plant Growth 565 



house, where the temperature was much higher than out-of-doors, 

 blossomed at the same time. The test plants behaved quite diflferently, 

 for blossoming was completely inhibited throughout the summer. More- 

 over, the growth of the controls has been considerably greater than that 

 of the test plants. See Plate 74. 



BEANS (PHASEOLUS VULGARIS L.) 



Three lots of seed of a tropical bean — two of which came from Are- 

 quipa, Peru, and one from Oruro, Bolivia— were planted together in 

 two boxes measuring 3 feet by 10 inches by 10 inches on June 16, and 

 one box was placed in the dark house June 24. Exposed to light from 

 9 a. m. to 4 p. m. According to Dr. D. N. Shoemaker this bean when 

 planted in the field at Washington has been found to make a very large 

 growth without blossoming till late in the fall, but when propagated in 

 the greenhouse in the winter months the plant promptly blossoms and 

 sets seed. The test plants blossomed July 21 to 23, and some of the 

 seed pods were mature by August 22, whereas the controls did not 

 blossom till October 11. The average height of the test plants was 4^ 

 to 5 feet and that of the controls 7 to 8 feet. See Plate 73. 



RAGWEED (ambrosia ARTEMISIIFOLIA L.) 



Exposed to light from 9 a. m. to 4 p. m. Observations based on 6 

 test plants and 6 controls. Small plants taken from the roadside were 

 transplanted to 6-inch pots on June 3, and a portion of these were im- 

 mediately placed in the dark house. Staminate heads were showing on 

 the test plants by June 17, and the anthers were shedding pollen freely 

 by July I. The controls did not begin blossoming till the last week in 

 August, which is the normal period for the appearance of first blossoms 

 on the plant. The average height of the test plants at the time of 

 blossoming was 8 to 9 inches, while that of the controls on the same date 

 was II inches and their final height 29 inches. The test plants were 

 returned permanently to normal light exposure on July i. See Plate 

 75, A. 



RADISH (RAPHANUS SATIVUS L.) 



Scarlet Geobe : ' 



Exposed to light from 9 a. m. to 4 p. m. Planted May 15, up May 19, 

 and placed in dark house on day of planting. The test plants grew more 

 slowly than the controls for a tim.e and then appeared to grow no further. 

 All but two of the test plants, of which there were a large number, be- 

 came diseased and finally died without forming seed stalks. The two 

 survivors developed a crown of large leaves, and the roots also reached 

 much larger proportions than those of the controls. Apparently en- 

 largement of the roots had not ceased as late as October 15, when one 



'Horticultural variety. 



