Description from Flora of China
Mesosphaerum brevipes (Poiteau) Kuntze.
Herbs erect, annual. Stems 50-100 cm, angles appressed pilose. Petiole ca. 5 mm; leaf blade ovate-oblong to lanceolate, 5-7 × 1.5-2 cm, adaxially olive green, abaxially greenish, pilose, base narrowly cuneate, margin serrate, apex acuminate. Capitula axillary, ca. 1 cm in diam.; peduncle 0.5-1.6 cm, densely appressed pilose; bracts lanceolate to subulate, 4-6 mm, margin entire. Calyx subcampanulate, 2.5-3 × ca. 1.5 mm, minutely hispid; teeth as long as tube, apex subulate; fruiting calyx dilated. Corolla white, ca. 3.5 mm, puberulent, throat to 1 mm wide; upper lip ca. 0.5 mm, lobes circular, reflexed; middle lobe of lower lip larger, concave, circular, ca. 1 mm, constricted at base, recurved; lateral lobes triangular, reflexed. Stamens slightly exserted. Nutlets dark brown, ovoid, ca. 1 × less than 0.5 mm, adaxially ribbed, with 2 basal white scars.
Open waste areas at low elevations. Hainan, Taiwan [North America, widespread tropical weed].