7. Alternanthera paronychioides A. St.-Hilaire, Voy. Distr. Diam. 2: 439. 1833 (as paronichyoides).
Smooth joyweed
Illecebrum ficoideum Jacquin, Select. Stirp. Amer. Hist., 88. 1763, not Linnaeus 1762
Herbs, perennial, 1-8 dm. Stems prostrate, villous, glabrate. Leaves sessile; blade elliptic, ovate-rhombic, or oval, 0.6-2.5 × 0.3-1.1 cm, apex acute or obtuse, villous, soon glabrate. Inflores-cences axillary, sessile; heads white, globose, 0.5-1 cm diam.; bracts less than 1/2 as long as tepals. Flowers: tepals monomorphic, white, lanceolate, 3-5 mm, apex acuminate, without rigid, spinose tips, hairs not barbed; stamens 5; anthers 3-5, globose; pseudostaminodes ligulate, shorter than filaments, margins entire or dentate. Utricles included within tepals, stramineous, orbiculate to rounded-obovate, 2-2.3 mm, apex truncate. Seeds lenticular, 1.2-1.5 mm.
Flowering spring-late fall, year-round in far south. Ballast ground, swamps, sandy places, limestone near salt water; 0-10 m; introduced, Ala., Del., Fla., Ga., La., Miss., N.J., N.C., Pa., S.C., Tenn., Tex.; Mexico; West Indies; Central America; South America; Asia; Africa; Pacific Islands.
Plants identified as Alternanthera paronychioides var. amazonica Huber have been collected on salt flats in central Louisiana. The specimens I have seen are not sufficiently distinct to warrant varietal recognition.
