1922] HARVEY—ARTIFICIAL LIGHT 449 
efficient, for all that is not used by the plants goes to heat. Since 
sunlight is not required, the rooms can be insulated much better 
against heat loss than a greenhouse. 
In a room 6X11 feet, lighted by 10-200 watt lamps, several 
vegetables were grown. The temperature was about 25°-30° C., not 
well controlled. The light intensity was about 380 lumens per 
square foot. Potatoes and tomatoes grew well, but were somewhat 
taller than normal. Early Ohio potatoes bloomed when the vines 
Fic. 1.—Cabbage, lettuce, potato, tomato, beans, peas, and a number of other 
plants growing in continuous artificial light; room 6X8 feet, lighted with lamps of 
2600 watts capacity. 
were 44 inches long. Boston marrow squash bloomed at 42 inches, 
but did not set fruit. Alaska peas bloomed at 18 inches and set 
good seed. Solanum niger set abundant fruit, beginning at 6 
inches, and continued fruiting up to 28 inches. Cabbage started 
heads at about 18 inches and showed some effects of etiolation. 
Buckwheat set normal seed at 20 inches. 
In another room 6 x8 feet, lighted by lamps with a total capacity 
of 2600 watts, the plants appeared much more normal than in the 
room just mentioned (fig. 1). The light intensity here was about 
680 lumens per square foot and the temperature 25°-30°C. Cabbage 
