Orthosiphon

Herbs or undershrubs, sometimes with tuberous roots. Leaves opposite or rarely ternate, coarsely crenate or dentate to subentire. Inflorescences terminal, spike-like, on main and sometimes on upper lateral branches; bracts small, persistent; flowers 1-6 in axils of each bract, forming 2-12-flowered verticils 10-20 mm apart. Calyx 5-toothed, 2-lipped; tube cylindric to campanulate; upper tooth broadly ovate-orbicular with margin +/- decurrent on tube; lower teeth subequal, ovate-deltoid, acuminate to subulate, 2 lowest usually longer than 2 laterals. Corolla bilabiate; tube narrowly to broadly cylindric, straight or curved; upper lip erect, 3- or 4-lobed; lower lip horizontal to recurved, concave to boat-shaped. Stamens 4, free, didynamous, declinate, exserted; lower pair arising near mouth; upper pair arising further back in corolla tube; filaments glabrous or pilose at base; anthers 1-thecous. Disc saucer-shaped, often with a ventral lobe. Style filiform, +/- capitate, lying together with and subequal to stamens. Nutlets suborbicular to oblong, glabrous. x = 7 (6, 11, 13) (polyploidy).