58 Diseases of Greenhouse Crops 



60 degrees will absorb far more light than if placed 

 at angles of 10 or 30 degrees. 



It has been the general belief that the light in 

 the hothouse was greatest nearest to the glass. Ex- 

 perience has disproved this. Modem houses are 

 built larger, which means a greater distance between 

 glass and plants. 



Effects of Various Colored Lights 



That plants require light for their normal de- 

 velopment and for the proper performance of their 

 function no one doubts. Crops grown outdoors 

 naturally receive their light from the sun's rays. 

 Plants within the greenhouse do not always receive 

 the rays of the sun in a normal way. As a result, 

 the health of these plants may often be impaired, 

 or the quality of the product greatly affected. The 

 researches of Flammarion* on this subject are of 

 particular interest to the greenhouse man. 



Temperature Influenced by the Color of 

 THE Glass 



Flammarion has shown that temperature is af- 

 fected by the color of the glass. Houses differen- 

 tiated by the following sorts of colored glass were 

 tried: blue, approaching closely to violet; red tra- 

 versed by a little orange; green and ordinary white 

 glass. These four houses were placed side by side 



* Flammarion, Camille. Experiment Station Record 10: X03-114, 



