Light in Greenhouse Culture 69 



ered with cloths of different textures. The arrange- 

 ment of the cloth and the amount of light penetrat- 

 ing it are shown in Table 1 1 . 



Table 11 



Method of Determining the Effect of Different 

 Light Intensities 





I 



2 



3 



4 





6 



Cloth Used 



Black 

 Duck 



Light 

 Canvas 



Cloth 

 {Black) 



Cham- 

 bray 



Light 

 Cham- 

 bray 



Voile 



No 

 Cover 



Fraction of normal light 

 ■capable of passing 



1/93 



or 

 n/93 



1/15 

 or 

 n/iS 



1/7 

 or 

 n/7 



1/5 

 or 



iign/s 



1/2 

 or 

 |n/a 



I 



or 

 n 



As an explanation to Table 11, in referring for 

 instance to column marked 2, n/ 1 5, we mean the 

 second section of the bed where light canvas cloth 

 (black) was used for shading, and where the light 

 capable of passing through was equivalent to 1/15 

 or ^/i5, I ox n represents the normal. The same 

 interpretation is given to the other sections of Table 

 11, all of which really correspond to the sections of 

 the bed experimented with, it being remembered 

 that I ox n represents normal light. 



Effect of Different Light Intensities on 

 Lettuce 



According to Shantz, lettuce could not grow in 

 section 1 under ^2/93 illumination, as the seedlings 

 died as soon as the reserve food material in the 

 cotyledons was consumed. In section 2, n/\$ 



