HYDEOCIIAEIDE^. 499 



LXXIX. HYDEOCHARIS FAMILY. HYDEOCHAEIDE^. 



Aquatic herbs, with undivided leaves, and mostly dioecious 

 flowers, enclosed when young in an involucre or upatlia of 1 to 

 3 leaves or bracts. Perianth of 3 or 6 segments, either all 

 petal-like or the 3 outer ones smaller and herbaceous, with a 

 tube adherent to the ovary at its base in the females, without 

 any tube in the males. Stamens in the males 3 to 12. Ovary 

 in the females inferior, 1-celled, with 3 parietal placentas, or 

 divided into 3, 6, or 9 cells. Styles 3, 6, or 9, with entire or 

 2-cleft stigmas. Fruit small, ripening under water, indehisceut. 

 Seeds several, without albumen. 



A small Order, widely diffused over the globe. 



Stem floating and branched, with small opposite or whorled leaves. 



Female perianth-tube long and thread-hke. Stigmas 3 . . . . 1. Elodea. 



Stem root-like, with floating tufts of orbicular leaves. Female peri- 

 anth-tube short, on a slender pedicel. Stigmas 6 .• "■ Feogbit. 



Stem scarcely any. Leaves tufted, succulent, radical. Female peri- 

 anth-tube short, on a stout pedicel. Stigmtis 6 3. Steatiotes. 



I. ELODEA. ELODEA. 



Stems submerged, branched, and leafy. Flowers sessile, the males with 

 9 stamens, tlie females with a long, thread-like perianth-tube. Style ad- 

 herent to the tube, with 3 notched or lobed stigmas. Ovary 1-celled, with 

 3 parietal placentas. 



A small genus, exclusively American. 



1. Canadian Elodea. Elodea canadensis, Eich. 

 {Anaeharis Alsinastrum, Bab. Man.) 



A dark green, much branched perennial, entirely floating under water. 

 Leaves numerous, opposite or in whorls of 3 or 4, sessile, linear-oblong, 

 transparent, 3 or 4 hues long. Female flowers, the only ones known in 

 this country, sessile in the upper axils, in a small, 2-lobed spatha; the 

 slender perianth-tube often 2 or 3 inches long, so as to attain the surface of 

 the water, where it terminates in 3 or 6 small, spreading segments. Male 

 flowers unknown as yet in this country, and seldom observed anywhere. 



In ponds, canals, and slow streams, abundant in North America, and 

 probably introduced from thence into JSritain, where it was first observed in 

 1847, in Yorkshire, Leicestershire, and near Berwick and Edinburgh. It 

 has since spread with great rapidity over many parts of England, especially 

 in the canals of Lincohashire and Cambridgeslure. Fl. summer and autumn. 



n. FROGBIT. HYDEOCHARIS. 

 A single species, distinguished as a genus from Stratiotes and others 

 more by its habit than by any very marked characters in the flower. 



1. Common Frogbit. Hydrocharis IMCorsus-ranse, Lum. 

 (Eng. Bot. t. 808.) 

 Stems floating, resembhng the runners of creeping plants, with floating 



