HIGHER PLANTS 



three inches long, they float up near the surface and there 

 they remain. The minute male and female flowers borne at 

 the bases of the leaves never rise above the water but the 

 stamens of the male flowers break off and float to the surface, 

 there shedding their pollen which "rains" down upon the 

 female flowers. Ceratophyllum's entire dependence upon water 

 to carry its pollen shows how much more truly aquatic it is 

 than most higher plants of the water. Toward autumn the 

 ends of its branches break off, float about for a time and 

 are finally pulled down to the bottom partly by their own 

 weight and partly by their "living freight of aquatic mollusks, 

 insects, and annelids." Such branches winter over on the 

 bottom but with the return of spring they float up again 

 and grow rapidly. 



Occurrence. — Common in ponds and slow streams. June- 

 August or September. Throughout North America except 

 in the extreme north. 



Animal associates. — Horn worts grow in ferny beds so thick 

 that they leave no place for any other plants. These horn- 

 wort forests are literally animated by a great population of 

 snails, worms, and small animals which feed upon one another 

 or upon the algae which cover the homworts. 



Water-lilies — Nymphceacece 



Spatterdock or yellow pond-lily, Nymphaea advena. — Al- 

 though yellow and white pond-lilies often Jive together the 

 yellow ones (Fig. 75) are commoner and thrive in many ponds 

 where white ones are not found at all. They grow in densely 

 populated shallows where pond-skaters dart about on what- 

 ever water they can find, where hundreds of spring-tails 

 make gray-black patches on the surface, and companies of 

 whirligig beetles come swinging in from open water (PI. II). 



Their leaves are stockier and more ovate than those of the 

 white lily. The flower is a yellow or yellow-green cup formed 

 of six overlapping sepals; yellow stamen-like petals encircle 



91 



