CONTROLLED ENVIRONMENTAL CONDITIONS 



319 



Figure 131. (Above) Petunias grown in spectral houses 2, 3, and 5. Tliis shows the 

 effect of growing a plant without the blue region (house 5) and without red (house 3). 

 (Below) Four-o'clock grown in spectral houses 2, 3, and 5. The "shade" plant was grown 

 outdoors under shading cloth at an intensity slightly higher than house 5. Roof plants 

 were grown in open sunlight. House 2 transmits the visible and ultraviolet regions, 

 house 3 glass transmits no red, and house 5 glass transmits no blue. 



have been published as yet. The south side of one of our regular green- 

 houses was later covered Avith Sunlit glass. This is a thin clear glass with 

 high transmission in all ranges of the solar spectrum. It transmits some 

 ultraviolet at 255 m/x and has 50 per cent transmission at 290 m^t. The 

 plants gro^vn in this greenhouse are not strikingly different from those 

 grown in an ordinary glass house. 



