1. Arenaria benthamii Fenzl ex Torrey & A. Gray, Fl. N. Amer. 1: 675. 1840.
Plants annual. Taproots filiform. Stems 1-40+, erect to ascending, branching, green, 10-30(-50) cm; internodes ± terete, mostly 1-10 times as long as leaves, dull, retrosely puberulent in 2 lines. Leaves usually connate proxi-mally, with scarious sheath 0.2-0.4 mm, petiolate (proximal leaves) or sessile; petiole 2-4 mm; blade 1-veined, vein ± weak abaxially, ovate (petiolate blades) or elliptic-lanceolate to oblanceolate, 5-15(-20) × 2-4 mm, herbaceous, margins undulate, scarious, shiny, sparsely ciliate especially proximally, apex acute to apiculate or cuspidate, often pustulate, glabrous; axillary leaf clusters absent. Inflorescences terminal, open, leafy, 3-50+-flowered cymes. Pedicels erect to reflexed in fruit, 10-40 mm, glabrous. Flowers: sepals green, 1-veined, vein obscure or prominent proximally, not keeled, elliptic to broadly ovate (herbaceous portion light green, ovate), 2-3.5 mm, to 4.5 mm in fruit, apex acute to acuminate, often pustulate, glabrous; petals elliptic, 1.5-3 mm, 1/ 3/ 4 times as long as sepals, apex obtuse. Capsules loosely to tightly enclosed by calyx, ovoid, 3-4 mm, 1 5-2 times as long as sepals. Seeds 20-30, ashy brown, broadly reniform, compressed, 0.5-0.6 mm, dull, minutely or prominently rounded-tuberculate.
Flowering late spring. Open woodlands, limestone slopes and outcrops; 0-400 m; La., N.Mex., Okla., Tex.; Mexico (Coahuila, Nuevo León).