Annual, rarely perennial, herb; stems erect, 5- ca. 30 cm tall, terete, often highly branched, flocculose-tomentose above. Leaves in whorls of up to ca. 15(-26) leaves per node; stipules silvery-white, scarious, aristate, multilacerate, 2-5 mm long, persistent; blade linear or linear-subulate, 3-15 x 0.2-0.3 mm, long-aristate with a distinctly differentiated apical arista, glabrous or sparsely pilose, sometimes mucilaginous. Inflorescence a many-flowered, dichasial cyme; pedicels 2-5 mm long, puberulent. Sepals usually 5, silvery-white, lanceolate, 2.5-3.5 mm long, acute to aristate, scarious; petals 5, sordid-white, entire or slightly dentate, obovate or ovate-oblong, 0.5-1 mm long, obtuse or denticulate, much shorter than sepals; stamens 5, filaments flattened, 0.5-1 mm long; ovary obovoid or ovoid-oblong, shortly stipitate, style to 0.5 mm long, 3-sulcate at apex. Capsule ellipsoid or obovoid, 1-2.5 mm long; seeds 2-6, cochleate, ca. 0.5 mm wide, minutely corrugated, pale brown.
Guianas present, Tropical and subtropical regions of the Old and New Worlds present
Tropical and subtropical regions of the Old and New Worlds; 23 collections studied, all from the Guianas (GU: 12; SU: 11).
Several specimens from Guyana and Suriname have been annotated as var. brasiliensis (Cambess.) Chodat & Hassl. by Olga Lakela; this variety, which occurs in Brazil and Paraguay, is said to be a perennial with woody napiform root and strongly revolute leaves, whereas typical
P. corymbosa is an annual with fibrous roots from a slender main root and flat or slightly revolute leaves. All specimens seen for this treatment conform to typical P. corymbosa. For a brief discussion of variation in this species, see Lakela (1962).