PLANTS: small, annual. STEMS: slender, erect or ascending, simple or sparingly branched, more or less angular when young. LEAVES: opposite, oblong-lanceolate to subulate, united at base by a fimbriate stipular sheath. FLOWERS: small, in terminal or axillary glomerules; calyx lobes 2-4, unequal, often conspicuously united at base, deciduous at maturity; corolla 4-lobed, salverform or nearly so. FRUIT: didymous, nutlets obovoid, separating at maturity. NOTES: 15 spp.; sw U.S.; Mex., C. Amer. (for W. Cruse). REFERENCES: Dempster, Lauramay T. 1995. Rubiaceae. J. Ariz. - Nev. Sci. 29(l): 29.