54° 



ECOLOGY 



Fig. 776 A 



Fig. 776 B 



Fig. 776. — Phototropism in the nasturtium {Tropaeoliim): 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 FtJLLER. 



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 {Typhu) ; Miller, Indiana. — Photograph supplied by Meyers. 



