BENDING OF HIGHER PLANTS TOWARD THE LIGHT 6l- 



Fig. 4. I. A vertical section of the light grader. The lens (a), which is a seg- 

 ment of a cylinder, has its longitudinal axis lying in the plane of the section; b, 

 stage; c, Nernst glower; d, non-reflecting background; e, mirror;/, light rays; g, 

 opaque screens. Distance from glower of lamp to stage, one meter. 



II. Stereographic view of light, lens, and image; a, lens; b, field of light pro- 

 duced by the image of the glower (c); d, opaque screen, which lies flat on lens and 

 contains a triangular opening which causes a gradation in the light intensity of 

 the field (b). 



hung a loose vertical curtain, which can be so opened that 

 observations can be made without admitting Hght. The 

 source of hght Is a Nernst glower, which Is parallel with the 

 minor axis of the lens. It is mounted In front of a small 

 opening In a light-proof box painted dead black Inside, 

 which thus forms a non-reflecting background. The glower 



