Alternanthera Sessilis

Annual or usually perennial herb; in drier situations with slender, more solid stems, prostrate, decumbent or erect, more or less much-branched, to c. 30 cm.; in wetter places ascending or most commonly prostrate with stems c. 0.1–1 m. long, rooting at the nodes, more or less fistular, with numerous lateral branches; when floating very fistular, the stems attaining a metre or more in length and over 1 mm. thick, with long clusters of whitish rootlets at the nodes.

Fruit glabrous, obcordate or cordate-orbicular, 2–2.5 mm. long, dark at maturity, strongly compressed with the margins each side of the seed not much thicker than the narrow, pale, yellowish keel, slightly longer to slightly shorter than the perianth.