FIELD BOOK OF PONDS AND STREAMS 



Fig. 8o. — Mare's-tail, Hippuris vulgaris. (From 

 Arber.) 



Occurrence. — In brackish or fresh ponds and slow streams. 

 Labrador to Alaska, south to Connecticut, the (Sreat Lakes 

 region, and the southwestern states. 



Bladderworts — Lentihulariacece 



Bladderwort, Utricularia vulgaris. — Although more innocent 

 looking plants than the sundews, the bladderworts (Fig. &2) 

 bear hundreds of death traps for minute water animals. 

 There are several species of them, all delicate, vine-like plants, 

 which float beneath the surface among the stems of water- 

 lilies, and pondweeds. Their presence is the sign of an 

 abundant population of protozoans, nematode worms, roti- 

 fers, and small crustaceans (PI. IV). ^ 



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