Acrocephalus Benth.

Annual herbs. Stems quadrangular. Leaves opposite or seemingly whorled by the presence of the leaves of underdeveloped lateral branchlets. Verticillasters agglomerated into terminal or axillary globose or ovoid spurious heads or cylindric terminal and upper axillary spurious spikes. Bracts imbricate. Flowers very small, sessile. Calyx ovoid (in fruit tubular), 7-nerved, base slightly gibbous; upper lip flat, entire; lower lip (in Mal. sp.) generally 4-toothed; throat naked. Corolla tube very short, subequally 5-lobed. Stamens 4, declinate, the lower pair slightly longer, glabrous; filaments free, toothless, included; anthers reniform, cells confluent. Disk small, equal-sided or gibbous. Style 2-fid. Nutlets minute, ellipsoid, smooth or glandular.