194 



PLANT PHYSIOLOGY 



until the intensity of light has attained the intensity of full 

 sunlight (the continuous curve in Fig. 56). In plants adapted 

 to shaded habitats, e.g., Oxalis (the broken curve in Fig. 56), 



Fig. 57. — Development of the shade plant Teucrium scorodonia (above) and of 

 the heliophilous plant Amaranthus retroflexus (below) under different light con- 

 ditions. The figures under the drawings show the growth under intensities 

 increased in the ratios 2 : 3 : 4 : 5, the last being full sunlight {redrawn from Combos) . 



assimilation increases until Kght has attained a comparatively 

 low intensity, or about one-tenth of full illumination. Further 

 increase of light remains without effect or even induces a depres- 



