437 



VOL. II.] ST. JOHN'S-WORT FAMILY 



2. Triadenum petiolatum (Walt.) 



Britton. Larger Marsh St. John's- 



wort. (Fig. 2465.) 



Hypericum petiolatum Walt. Fl. Car. 191. 1788. 

 Elodea petiolata Pursh, Fl. Am. Sept. 379. 1814. 



Similar to the preceding species, but often 

 more branched and taller; leaves generally 

 longer (2 / ~5 / ), petioled, or the upper sessile, 

 not clasping, pale beneath; flower-clusters 

 axillary and terminal, sessile or very short- 

 peduncled. 



In swamps, New Jersey and Maryland to Flor- 

 ida, west to Arkansas and Louisiana. July-Aug. 



Family 77. ELATINACEAE Lindl. Nat. Syst. Ed. 2, 88. 1836. 



WATER-WORT FAMILY. 



Low herbs, sometimes woody in tropical regions, with opposite or verticillate 

 stipulate entire or serrate leaves, and small axillary solitary or fascicled flowers. 

 Flowers regular, perfect. Sepals 2-5, imbricated. Petals the same number, 

 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 septi- 

 cidal dehiscence. Placentae central. Seed-coat crustaceous, rugose or ribbed. 



About 25 species, of wide geographic distribution. 



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



Flowers mainly 5-merous; pubescent ascending or diffuse herbs. 2. Bergia. 



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 eo , straight, 

 or slightly curved, striate longitudinally and transversely. [Greek, fir-like, with reference 

 to the leaves.] 



About 9 species, natives of temperate and warm regions. In addition to the following, another 

 occurs in California. 



Petals and stamens 2; 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) Am. Water-wort. Mud-purslane. (Fig. 2466.) 



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

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



Erect or spreading, tufted, aquatic or terrestrial, %'-i%' 

 long, often submerged. Leaves obovate, obtuse, i // -^ // 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 y^" in diameter; seeds %" to nearly l /* ff long, 

 slightly curved, marked by 9-10 longitudinal striae and 20- 

 30 cross-bars. 



Margins of ponds and slow streams, Ontario and New Hampshire to Illinois, south to Virginia 

 and Texas. Also in Colorado and Oregon. Summer. 



