THE HORTICULTURAL SOCIETY OF NEW YORK 



The ten 500-watt gas-filled Mazda lamps were hung in a row 

 36 inches above the surface of the bench. Each reflector-socket 

 was arranged ij4 ft- between sections so that the edges of the re- 

 flectors were approximately Y^. ft. from each other. The adjust- 

 ment range was i to 8 ft. and was kept constant for 4 weeks at 

 36 inches above the bench. On account of the increased tempera- 

 ture during the day and the high temperature under the lights, the 

 adjustment was made 4 ft. above the surface of the bench. 



The lamps were kept burning continuously from 9:00 p. m. 

 until 2:00 A. M. When reference to artificial light is made it 

 should be understood that during the day the plants were exposed 

 to the sun as were the check plants. 



During the test, twelve days out of the thirty-five were cloudy. 



The average maximum temperature of circulating air during the 

 period of test was 91.3° F. for the test plants and 95.8° F. for 

 the check, while the average minimum temperatures were 64.9° F. 

 for the test plants and 73.7° F. for the check plants. In the rays 

 of the lamps according to the Brown recording thermometers, the 

 temperature averaged about 22° F. higher than the average range 

 during the day, the maximum temperature being attained at 2 a. m. 

 The root temperatures averaged 60.5° F. for the test plants and 

 57.5° F. for the check plants. These readings were taken at 

 9 a. m. before the plants were watered. The root temperature was 

 raised about 8° F. when the lights were on five hours, as shown by 

 readings taken at 2 a. m. All readings were taken with Fahren- 

 heit and Centigrade thermometers properly calibrated and checked. 



Records of the average height were taken weekly. Individual 

 plants tend to vary materially when raised under the same condi- 

 tions so that an average of each type of plant under the light was 

 taken and also an average of the growth of the plant of each type 

 under sunlight only. 



Water was applied to the plants under the lamps on an average 

 of 7 times per week, and the plants under normal light were wa- 

 tered 7 times per week. During the last week of the test the plants 

 under the lamps were watered 9 times per week while the plants 

 under normal light were watered 7 times per week. 



Chemical tests of the plants for chlorophyl and starch contents 



40 



