TAMARICACEAE 783 



FAMILY 3. ELATINACEAE Lindl. WATER-WORT FAMILY. 



Herbs or shrubby plants, with erect or creeping stems. Leaves opposite or 

 whorled, with stipules. Flowers perfect, regular, solitary or clustered in the 

 axils. Calyx of 2-5 imbricated sepals. Corolla of as many hypogynous petals 

 as there are sepals. Androecium of 2-5 or sometimes 10 stamens inserted with 

 the petals. Filaments slender. Gynoecium of 2-5 united carpels. Ovary 

 2-5-celled with central placentae. Stigmas 2-5, distinct, introrse. Ovules sev- 

 eral, anatropous. Fruit a capsule opening septicidally. Seeds with a ribbed or 

 wrinkled crustaceous testa. 



Plants glabrous : flowers 2-4-merous : sepals membranous, obtuse. 1. ELATIXE. 



Plants pubescent : flowers 5-merous : sepals with a thick center, acute or acuminate. 2. BERGIA. 



1. ELATINE L. 



Low, soft, often aquatic herbs, with glabrous foliage. Leaves opposite or whorled : 

 blades commonly entire. Flowers usually solitary in the axils. Sepals 2-4, membranous, 

 obtuse, nerveless. Petals as many as the sepals. Stamens as many as the sepals or twice 

 as many. Ovary 2-4- celled : styles 2-4. Capsule membranous, subglobose, 2-4-valved. 

 WATER-WORT. MUD-PURSLANE. 



1. Elatine Americana (Pursh) Arn. Terrestrial or aquatic, often submerged. 

 Stems tufted, 1-4 cm. long, erect or spreading : leaf-blades obovate or oblong-obovate, 2-6 

 mm. long, obtuse : flowers minute, sessile in the axils : sepals 2, obtuse : petals 2 : stamens 

 2, barely as long as the perianth, or sepals, petals and stamens 3 in terrestrial forms : cap- 

 sules subglobose, nearly 1 mm. diameter: seeds slightly curved, 0.5-0.7 mm. long, with 

 9-10 striae and 20-30 cross bars. 



On margins of ponds and in slow streams, Ontario to Oregon, Virginia, Texas and Colorado. 

 Summer. 



2. BERGIA L. 



Herbs or shrubby plants, with erect or prostrate stems and pubescent foliage. Leaves 

 opposite : blades toothed or entire, sometimes thickish. Flowers solitary in the axils or 

 clustered. Sepals usually 5, acute, with a herbaceous or ribbed middle, and hyaline edges. 

 Petals usually 5. Stamens as many as there are sepals. Ovary 5-celled : styles 5. Cap- 

 sule somewhat crustaceous, septicidally or septifragally 5-valved. 



1. Bergia Texana (Hook.) Seubert. Stems branched at the base, the branches 

 prostrate or ascending, 1-3 dm. long, more or less forked : leaf -blades elliptic or spatulate- 

 elliptic, 1-2.5 cm. long, acute or obtuse, serrulate, prominently nerved beneath in age, 

 narrowed into short petioles : flowers solitary or 2-3 together in the axils : sepals ovate or 

 ovate-lanceolate, 2.5-3 mm. long, acuminate, denticulate : petals oblong or slightly broad- 

 ened upward, obtuse, shorter than the sepals : capsules subglobose, about 2 mm. in diam- 

 eter : seeds oblong, the striae connected by cross bars. 



In alluvial or sandy soil, Illinois to California and Texas. Summer. 



FAMILY 4. TAMARICACEAE Lindl. TAMAEIX FAMILY. 



Shrubs or trees, or partially woody herbs. Leaves alternate, without stipules, 

 relatively small or scale-like, entire, often imbricated. Flowers mainly perfect, 

 regular, usually in spikes, racemes or panicles. Calyx of 5, or rarely 4 or 6, 

 imbricated sepals. Corolla of 5, or rarely 4 or 6, distinct imbricated petals. 

 Disk 10-lobed or obsolete. Androecium of 5-many stamens. Filaments dis- 

 tinct, free. Anthers opening lengthwise. Gynoecium 2-5-carpellary, superior. 

 Ovary 1-celled, with 3-5 basal placentae. Stigmas 3-5, distinct. Ovules 2- 

 many on each placenta. Fruit a capsule. Seeds erect,, each terminating in a 

 coma. 



1. TAMARIX L. 



Shrubs or trees, with irregularly and widely branching stems, the wood firm. Leaves 

 small, scale-like, clasping or sheathing. Flowers in dense spikes, racemes or panicles. 

 Sepals 4-5, or rarely 6, distinct. Corolla white or pink. Petals inserted under the lobed 

 disk, distinct or essentially so. Stamens 5-10, or rarely 4 or 12 : filaments not adnate 



