Plants green, sometimes purple tinged, homophyllous or hetero-phyllous, sometimes subsucculent. Stems prostrate to ascending, sometimes zigzagged, branched from base, not wiry, 5-50 cm. Leaves: ocrea 2.5-12 mm, proximal part funnelform, distal part soon disintegrating, nearly completely deciduous or fibers persistent; petiole 2-7 mm; blade light green, sometimes purple tinged, elliptic to elliptic-obovate or obovate, 8-30(-50) × 4-15(-25) mm, margins flat, apex acute to obtuse; middle stem leaves 1.1-2.1(-3.4) times as long as adjacent branch leaves, distal leaves overtopping flowers. Inflorescences axillary; cymes uniformly distributed, 1-7(-10)-flowered. Pedicels enclosed in or sometimes exserted from ocreae, 1-2.5 mm. Flowers closed; perianth (2.2-)2.5-4.5 mm; tube 23-38% of perianth length; tepals initially overlapping, pushed apart as achene develops, green, margins white to pink, petaloid, not keeled, oblong, cucullate; midveins branched, sometimes not visible; stamens 6-8. Achenes exserted from perianth, brown to dark brown, broadly ovate to ovate-lanceolate, (2-)3-gonous, (1.8-)2-3.7(-4.5) mm, faces subequal or unequal, flat to concave, apex beaked, edges strongly concave, shiny to dull, roughened, rarely obscurely tubercled; late-season achenes common, 4-6 mm.
Prostrate to ascending, homophyllous annual to 5 dm, with relatively few, divergent branches; lvs elliptic-oblong to oblanceolate, 1-4 cm נ3-10 mm; ocreae seldom over 4 mm, lacerate, brown, the pedicels included or barely exsert; mature perianth 3-5 mm, cleft nearly to the base, its segments oblong, obtuse, cucullate (at least the outer), with white or pink margins, after anthesis appressed to the achene; achenes 2.8-4 mm, broadly short-beaked distally, finely granular- roughened, included (to 5 mm and exsert in late season); 2n=40, 60. Sea-beaches and margins of salt- marshes; Lab. and Nf. to Me., and on the n. Pacific coast. (P. allocarpum)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.