LIFE IN PONDS AND STREAMS 



from it. Sometimes it is gay with the rose-colored flowers 

 of Polygonum amphibium (Fig. 73). In the deeper water, 

 the ribbony leaves of pond weeds and fresh water eelgrass 

 stream upward from the bottom. There also may be the 

 submerged meadows of homwort and just below the surface 

 the little vine-like liverworts, Riccia (Fig. 52), and the blad- 

 derworts, Utricularia (Fig. 82). 



Fig. 19. — Bottom-dwellers: i, mayfly (CcBnis); 2, 

 tubes of Tubifex; 3, worm (Nais) ; 4, dragonfly {Li- 

 bellula) . 



The animals which live near shore are even more varied 

 and more numerous than the plants. On the underside of 

 a single lily pad (Fig. 18) are snails, small red water-mites, 

 tube-dwelling rotifers of the genus Melicerta (Fig. 10^), and 

 numerous midge larvag. These same lily pa,ds are so many 

 hundreds of floating hatcheries for the eggs of snails, mites, 

 beetles, and other water insects. All the plant stems are 

 coated with a green slime of algae, the food of pond-snails 

 and countless numbers of little tube-dwelling worms. Colo- 

 nies of fresh water sponges and bryozoans encircle the stems 

 and spread over the under surfaces of leaves. One sweep 

 of the net will bring up insect carnivores — larvae of tiger- 

 beetles, water-bugs, dragonfly and damselfly nymphs. 



15 



