A GUIDE TO THE WILD FLOWERS 305 



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934. Eel-grass. Vallisneria spiralis. (Vallisneriaceae.) A 

 slender, submerged aquatic with tape-like leaves, often many 

 feet long, and about ^ in. wide. The length varies with the 

 rapidity of the stream flow. For a description of the ex- 

 traordinary flowers see next to the last paragraph under 

 No. 926. In streams almost throughout North America. Oc- 

 casionally in brackish water. Fig. 934. Called also wild celery 

 and a common food of wild ducks. 



935- Water-fennel. Callitriche palustris. {Callitrichaceae.) 

 A submerged aquatic, very rarely with floating leaves. Leaves 

 ^-i in. long, slightly notched at the tip, narrow, opposite. 

 Flowers minute, without petals, solitary at the leaf joints, the 

 tiny fruit lobed. Usually in running water, nearly through- 

 out the world. Fig. 935. There are several other species. 

 936. Leafy Pondweed. Potamogeton foliosus. (Zannichel- 

 liaceae.) A submerged aquatic, the stem often 3 ft. long or 

 more, much branched. Leaves 1-2 in. long, about ^^2 i"- wide, 

 distinctly 3-veined. Flowers greenish, inconspicuous, in small 

 stalked clusters, followed by tiny nut-like fruits. In ponds 

 and streams. Nova Scotia to Florida, and westward. Fig. 



936. There are many closely related submerged Pondweeds. 



937. Water-weed. Philotria canadensis. {Elodea canadensis.) 

 (Vallisneriaceae.) A submerged aquatic frequently in great 

 masses, and in England known as Babington's Curse because 

 of its habit of choking streams and ponds. Leaves mostly 3 

 or 4 at each joint, linear or oblong, J4-/^ i"- ^o"g undivided, 

 either smooth margined or with minute teeth. Flowers 

 minute, whitish, some of them reaching the surface at matu- 



