PLATE 75 



A. — Ragweed. Plants on left exposed to light from 9 a. m. to 4 p. m. daily. Pollen 

 shedding freely from the staminate spikes when photographed July 9, 1919. Plants on 

 right left out of doors as controls. Showed no signs of flowering when photographed. 



B. — Radish. Plants in box on left exposed to light from 9 a. m. to 4 p. m. daily. 

 No indications of seed stalks when photographed August 19. Plants in box on right 

 left out of doors during the test. Bore an abundance of full-grown seed pods when 

 photographed. 



