ZONAL DISTRIBUTIOiY OF PLANTS. 



407 



overhanging willows. On the left, pond-weeds (Potamogeton 

 natans) and the yellow water lily, or spatter-dock (nuphar), 



Fig. 500. 

 Yellow water lily on jutting ann in stream. {Photograph by the author.) 



float their leaves and flowers on the quiet water, while the small 

 yellow flowers of the mud plantain (Heteranthera graminifolia) 

 glitter in the sunlight. The arrow-leaf (Sagittaria heterophylla, 



