314 



GROWTH OF PLANTS 



Spectral Greenhouses 



Fig. 127 shows the five spectral greenhouses used by Popp ^^ in his investi- 

 gations of the effect of spectral range of light on the growth of plants. 

 These houses were numbered successively from right to left. The light 

 transmission curves of the several houses are shown in Fig. 128. House 1 



£//fr-a-y/o/etAVlBl G Xt\0\Rcd\l-R 

 fo Aoo 4oo Aoo eoo Too ..., /, o 



U/ai/e Lenpif/f Jr? mju. 



Figure 128. Transmission curves of glasses in the visible and ultraviolet. Figures 

 on curves represent house numbers: 1, is ordinary greenhouse glass (house 1); 2, is Corn- 

 ing glass G86B (house 2); 3, is Coming's Noviol O (house 3); 4, is Coming's Noviol 

 C (house 4); 5, is Coming glass G34 (house 5). 



is window glass and cuts out all ultraviolet shorter than 312 m/x; house 2 

 is an ultraviolet-transmitting glass which cuts out ultraviolet shorter than 

 296 m/i; house 3 cuts out practically all the ultraviolet rays 389 mju and 

 shorter; house 4 cuts out all ultraviolet, violet, and part of blue up to 

 472 m^; while house 5 cuts out all the ultraviolet, violet, blue, and the 

 shorter green up to 529 m^. Table 34 shows the percentage of total solar 

 energy transmitted by the glasses on each of the five houses. For details 



Table 34. Relative Transmission of Total Intensity of Light by Glasses in Different 



Houses 



