PLANTS: Annuals or perennial herbs, rarely low shrubs. STEMS: terete or 4-angled. LEAVES: opposite with connecting fimbriate stipules. INFLORESCENCE: 1-several flowers in axillary glomerules. FLOWERS: small; calyx 2-4 dentate; corolla funnelform, 4-lobed; stamens 4. FRUIT: 2 nutlets, the calyx teeth persistent. NOTES: Ca. 50 spp. mostly of warmer parts of Amer., a few in Afr. (Greek: diodos = a thoroughfare, because often found growing by the wayside). REFERENCES: Dempster, Lauramay T. 1995. Rubiaceae. J. Ariz. - Nev. Sci. 29(l): 29.
Fls mostly 4-merous; sep 2-4, sometimes very unequal; cor salverform or funnelform, with slender tube and 4 short lobes; ovary bilocular, with a single axile ovule in each locule; fr dry, splitting into 2 nutlets; herbs, ours low and branched, with narrow lvs and small fls sessile in the axils. 50, mainly warm regions.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.