ELATINACEAE. 



VOL. II. 



hypogynous. Stamens the same number or twice as many. Ovary 2-5-celled; 

 styles 2-5, stigmatic at the apex; ovules oo, anatropous. Capsule with septicidal 

 clehiscence. Placentae central. Seed-coat crustaceous, rugose or ribbed. 



About 30 species, of wide geographic distribution. 



Flowers 2-4-merous ; glabrous aquatic or creeping herbs. i. Elatine. 



Flowers mainly s-merous ; pubescent ascending or diffuse herbs. 2. 



i. ELATINE L. Sp. PI. 367. 1753. 



Small glabrous or glabrate aquatic or creeping herbs, with opposite or verticillate leaves, 

 and minute axillary mainly solitary flowers. Sepals 2-4, persistent, membranous, not ribbed. 

 Petals of the same number, hypogynous. Stamens of the same number or twice as many. 

 Styles or stigmas 2-4. Pod membranous, globose, 2-4-valved. Seeds oo, straight, or slightly 

 curved, striate longitudinally and transversely. [Greek, fir-like, with reference to the leaves.] 



About 10 species, natives of temperate and warm regions. In addition to the following, another 

 occurs in California and one in Montana. Type species: Elatine Hydropiper L. 



Petals and stamens2 ; seeds distinctly sculptured. 



Leaves obovate ; seeds with 9-10 longitudinal and 20-30 transverse striae, i. E. americana. 



Leaves oblong or oval; seeds with 6-7 longitudinal and 10-12 transverse striae. 



2. E. brachysperma. 

 Petals and stamens mostly 3 ; seeds little sculptured. 3. E. triandra. 



i. Elatine americana (Pursh) Arn. Water-wort. Mud-purslane. Fig. 2905. 



Peplis americana Pursh, Fl. Am. Sept. 238. 1814. 

 Elatine americana Arn. Edinb. Journ. Sci. i : 430. 1830. 



Erect or spreading, tufted, aquatic or terrestrial, \'-\\' long, 

 often submerged. Leaves obovate, obtuse, i"-3" long, i" 

 wide or less ; flowers sessile, axillary, minute, rarely opening 

 in the submerged forms; sepals, petals, stamens and stigmas 2 

 (rarely 3 in the terrestrial forms) ; capsule globose, nearly 4" 

 in diameter ; seeds i" to nearly V long, slightly curved, marked 

 by 9-10 longitudinal striae and 20-30 cross-bars. 



Margins of ponds and slow streams, Quebec to British Colum- 

 bia, Virginia, Missouri, Texas and Mexico. Summer. 



2. Elatine brachysperma A. Gray. Short-seeded Water- wort. _Fig. 2906. 



Elatine brachysperma A. Gray, Proc. Am. Acad. 13: 361. 1878. 



Terrestrial 'or sometimes submerged, spreading, tufted, i'-2' long. 

 Leaves oblong, oval or lanceolate, narrowed at the base, 2"-$" long, 

 about i" wide, obtuse; flowers sessile, axillary, minute ; sepals, petals, 

 stamens and stigmas mainly 2; capsule nearly as in the preceding 

 species ; seeds short-oblong, nearly straight, about \" long, marked 

 by 6-7 longitudinal striae and 10-12 cross-bars. 



Margins of ponds, Illinois and California, doubtless occurring between 

 these limits. Summer. 



3. Elatine triandra Schk. Long-stemmed 

 Water-wort. Fig. 2907. 



Elatine triandra Schk. Bot. Hand, i: 345. 1791. 



Flaccid, tufted, immersed or creeping, stems 2'-4' 

 long, much branched. Leaves oblong or oblanceo- 

 late, very thin, obtuse, 2"-4" long, i" wide, narrowed 

 at the base ; flowers minute, axillary, sessile ; sepals 

 commonly 2; petals, stamens and stigmas 3; seeds 

 slightly curved, about the size of those of E. ameri- 

 cana, slightly marked longitudinally and transversely. 



Ponds, Illinois, South Dakota and Nebraska to Wash- 

 ington. Also in Europe. Summer. 



