EL A TINA CEA E. 629 



4. TRIADENUM Raf. 



Perennial marsh herbs, with entire oblong oval or ovate leaves, and pink or 

 greenish purple flowers in terminal cymes, or also axillary. Calyx of 5 equal per- 

 sistent sepals. Petals 5, not contorted. Stamens 9, or sometimes more, in 3 sets, 

 the sets alternating with 3 large hypogynous glands. Ovary 3-celled; styles 3. 

 Capsule oblong-conic, much longer than the sepals. [Greek, three glands.] Two 

 species, natives of E. N. Am. 



Leaves sessile; flower-clusters peduncled. i. T. Virginicum. 



Leaves short-petioled ; flower-clusters nearly sessile. 2. T. petiolatum. 



1. Triadenum Virginicum (L.) Raf. MARSH ST. JOHN'S-WORT. (I. F. f. 

 2464.) Nearly simple, 3-5 dm. high. Leaves sessile or cordate-clasping, ovate or 

 oblong, 2-6 cm. long, very obtuse, sometimes emarginate, glaucous beneath, black- 

 dotted; flowers 12-16 mm. broad, in leafy clusters; sepals acute, shorter than the 

 straight petals; stamens 9 or more, united in 3 sets; styles 3, distinct; capsule ob- 

 long, 8-10 mm. long, acute, red-purple. In swamps, Lab. to Fla., Man., Neb. and 

 La. July-Sept. 



2. Triadenum petiolatum (Walt.) Britton. LARGER MARSH ST. JOHN'S- 

 WORT. (I. F. f. 2465.) Similar to the preceding, but often more branched and 

 taller; leaves generally longer, petioled, or the upper sessile, not clasping, pale 

 beneath; flower-clusters sessile or very short peduncled. In swamps, N. J. and 

 Md. to Fla., Ark. and La. July- Aug. 



Family 3. ELATINACEAE Lindl. 

 Water -wort Family. 



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

 verticillate stipulate leaves, and small axillary regular perfect flowers. 

 Sepals 2-5, imbricated. Petals the same number, hypogynous. Stamens 

 the same number or twice as many. Ovary 2-5-celled ; styles 2-5, stig- 

 matic at the apex ; ovules oo , anatropous. Capsule with septicidal dehis- 

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

 About 25 species, of wide 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. 



Small glabrous or glabrate aquatic or creeping herbs, with minute mainly soli- 

 tary flowers. Sepals 2-4, persistent membranous, not ribbed. 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 9 species, of temperate and warm regions. In addition to the following, 

 another occurs in Cal. 



Petals and stamens 2 ; seeds distinctly sculptured. 



Leaves obovate ; seeds with 9-10 longitudinal and 20-30 transverse striae. 



1. 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. 



1. Elatine Americana (Pursh) Arn. WATER-WORT. MUD-PURSLANE. (I. F. 

 f. 2466.) Tufted, aquatic or terrestrial, 1-4 cm. long. Leaves obtuse, 2-6 mm. 

 long, 2 mm. wide or less; flowers sessile, minute, rarely opening in the submerged 

 forms; sepals, petals, stamens and stigmas 2 (rarely 3 in the terrestrial forms); 

 capsule globose, nearly I mm. in diameter; seeds 0.5-1 mm. long, slightly curved. 

 Margins of ponds and slow streams, Me. and Ont. to Va., Mo. and Tex. Also in 

 Colo, and Ore. Summer. 



2. Elatine brachysperma A. Gray. SHORT-SEEDED WATER-WORT. (I. F. f. 

 2467.) Terrestrial or sometimes submerged, spreading, tufted, 2-5 cm. long. 

 Leaves oblong, oval or lanceolate, narrowed at the base, 4-6 mm. long, about 



