3.
Alternanthera philoxeroides
(Martius) Grisebach, Abh. Königl. Ges. Wiss. Göttingen. 24: 36. 1879.
Alligatorweed
Bucholzia philoxeroides
Martius, Beitr. Amarantac., 107. 1825;
Achyranthes philoxeroides
(Martius) Standley
Herbs,
perennial, aquatic to semiterrestrial, stoloniferous, to 50 dm.
Stems
prostrate, forming mats, often fistulose, glabrous.
Leaves
sessile; blade narrowly elliptic, elliptic, or oblanceolate, 3.5-7.1 × 0.5-2 cm, herbaceous, apex acute to obtuse, glabrous.
Inflorescences
terminal and axillary, pedunculate; heads white, globose, 1.4-1.7 cm diam.; bracts not keeled, less than
1
/2 as long as tepals.
Flowers:
tepals monomorphic, white, lanceolate or oblong, 6 mm, apex acute, glabrous; stamens 5; pseudostaminodes ligulate.
Utricles
not seen.
Seeds
not seen.
Flowering early spring-summer. Ponds, ditches, streams, bayous; 0-200 m; introduced; Ala., Ark., Calif., Fla., Ga., Ill., Ky., La., Miss., N.C., S.C., Tenn., Tex., Va.; West Indies; native to South America.
Alternanthera philoxerioides
is said to reproduce only vegetatively in North America. I have seen no fruit or seed.
