3(1). Flowers irregular; calyx gibbous or spurred at base; petals unequal 



7. Cuphea 



3. Flowers regular or nearly so, symmetrical (4) 



4(3). Hypanthium elongated, cylindrical or tubular 3. Lythrum 



4. Hypanthium campanulate or turbinate, becoming hemispheric or globose (5) 



5(4). Flowers two or more in leaf axils; capsules bursting irregularly 



4. Ammannia 



5. Flowers solitary in leaf axils; capsules indehiscent or regularly dehiscent (6) 



6(5). Petals wanting; capsules indehiscent; submersed aquatic plants 5. Peplis 



6. Petals present; capsules dehiscent; terrestrial or marsh plants (7) 



7(6). Flowers sessile; capsules septicidally dehiscent 6. Rotala 



7. Flowers pedunculate; capsules variously dehiscent 2. Heimia 



1. Decodon J. F. Gmel. 

 A monotypic genus. 



1. Decodon verticillatus (L.) Ell. Water-willow, swamp-loosestrife. Fig. 538. 



Perennial herb or suffrutescent, smooth or downy; stems 4- to 6-sided, to 25 dm. 

 long, recurved-arching and rooting at tips, the bark of submersed parts spongy- 

 thickened; leaves shortly petioled, opposite or whorled, elliptic-lanceolate to 

 lanceolate, acute to subacuminate, to about 1 dm. long and 4 cm. wide, the upper 

 ones with clustered pedicelled flowers in their axils; flowers trimorphous; calyx 

 with 5 to 7 erect teeth and as many longer and spreading terete hornlike processes 

 at the sinuses; petals 5, cuneate-lanceolate, magenta, crinkly, about 12 mm. long; 

 stamens 10, of 2 lengths, exserted; style filiform, about 14 mm. long; capsule glo- 

 bose, 3- to 5-celled, loculicidal, black, 3-5 mm. in diameter. 



In swamps, shallow pools, in and on margin of ponds and lakes in e. Tex. (Wood, 

 Hardin, Madison and Cass cos.), July-Oct.; from Fla. to Tex., n. to N.E., N.Y., 

 s. Ont. and s. 111. 



The characteristic of the stems rooting at their tips enables the plant to spread 

 rapidly. They are thus capable of forming mats over water over which other plant 

 species may take root, 



2. Heimia Link & Otto 



Slender deciduous herbs or shrubs; leaves opposite or with some alternate, 

 exstipulate; flowers pedunculate, solitary in the axils of the leaves; calyx campanu- 

 late, with hornlike spreading processes between the lobes; petals 5 to 7; stamens 10 

 to 18; style slender, the stigma capitate; capsule 4-celled. 



Three species from Texas south to Argentina. 



1. Leaves tapering to a sessile or short-petioled base; peduncle stout, about 2 

 mm. long, the bracts elliptic-oblanceolate and about 4 mm. long 

 and 2 mm. wide; petals yellow 1. H. salicifolia. 



1. Leaves auricled at base; peduncle filiform, more than 1 cm. long, the bracts 

 ovate and about 2 mm. long and 1 mm. wide; petals pink to 

 purple 2. H. longipes. 



1. Heimia salicifoUa (H.B.K.) Link & Otto. Hachinal. Fig. 539. 



Shrub to 3 m. high, forming clumps, usually much smaller, glabrous throughout: 

 leaves mostly opposite, sessile to short-petioled, linear-oblanceolate to linear- 

 lanceolate or lanceolate, to about 5 cm. long and 1 cm. wide, obtuse to acute at 

 apex; flowers solitary and short-pedunculate in the axils, inodorous; calyx campanu- 

 late, 5-9 mm. long, with triangular acuminate lobes that become closely connivent 

 over the capsule; petals 5 to 7, orange-yellow, oval, 12-17 mm. long, fugacious; 



1157 



