H. Schum., Beskr. Guiana Pl. 421.1827
P. niruri L. var. amarus (H. Schum. & Thonn.) Leandri
Monoecious herb, 10-50 cm tall, glabrous; branchlets deciduous, 4-10 cm long, very slender. Leaves alternate, simple, thin; stipules lanceolate, ca 1 mm long; petioles to 0.5 mm long; blades elliptic-oblong, ± rounded at both ends, 5-11 mm long, 3-6 mm wide. Flowers minute, apetalous, greenish, 5-parted, usually 2 in each axil, the lowermost axils with staminate flowers, the others with 1 staminate and 1 pistillate flower; staminate flowers on pedicels 0.5-1.3 mm long; calyx lobes ± ovate, ca 0.5 mm long; stamens (2) 3; filaments connate into a column ca 0.3 mm long; pistillate flowers on pedicels to 1-2 mm long in fruit; calyx lobes obovate-oblong, to 1 mm long; disk flat, 5-lobed; ovary 3-carpellate, 2 ovules per locule; styles 3, free, ca 0.2 mm long, bifid at apex. Capsules globular, with 3 cocci, ca 2 mm diam, dehiscent, leaving persistent columella; seeds 2 per locule, trigonous, ca 1 mm long. Shattuck 398.
Collected once by Shattuck, but not seen in recent years on the island; to be expected as a weed in clearings. Seasonal behavior not determined. The few specimens seen had flowers and fruits in the dry season. Throughout the tropics. In Panama, known from tropical moist forest in the Canal Zone (both slopes), Chiriqui, and Panama.