CONTROLLED ENVIRONMENTAL CONDITIONS 



299 



Figure 120 (continued). C, Cucumber. Two pots (at left) grown in control green- 

 house. Two {at center) in gantry crane house with dayhght plus 6 hours of artificial 

 light each night plus ten times the normal CO2. Two {at right) same as center except 

 no extra gas. Plants are one month old from seed. D, Barley grown at a high tem- 

 perature, 78° F (26° C). The two pots of plants at left were grown in the control 

 greenhouse, two at center in the gantry crane greenhouse with daylight plus 6 hours sup- 

 plementary lighting plus a higher concentration of CO2, the two right same as center 

 except no extra gas. Age from seed, 40 days. 



light. Indeed, it is a question whether green plants will grow normally during 

 their entire life period under any narrow band of the visible spectrum. If 

 they ^vill, it is probably under bands in the blue or violet. This region has 

 as yet not been produced in sufficient intensity to give good growth. 



