54 



ECOLOGY 



FIG. 776 A 



FIG. 776 B 



FIG. 776. Phototropism in the nasturtium (Tropaeolum) : A, a plant that has 

 been exposed since germination to ordinary greenhouse illumination ; the diaphototropic 

 leaves face upward in such a position that they receive the maximum amount of incident 

 light; B, the same plant after exposure for six hours to one-sided illumination. Pho- 

 tographs by FULLER. 



FIG. 777. A pond margin with water lilies (Castalia); note that the leaves are 

 strictly horizontal, except in the background, where they are growing so close together 

 that their edges are upturned; shoreward from the water lilies are bulrushes (Scirpus) 

 and cattails (Typha); Miller, Indiana. Photograph supplied by MEYERS. 



