PLANT: Annual taprooted herbs or suffrutescent perennials, pubescent; stems erect or decumbent at base, freely branched. LEAVES: petiolate or subsessile; blades linear to ovate; margins entire or dentate, rarely lobed. INFLORESCENCE: panicles of cymes; bracts leafy or reduced. FLOWERS: pedicellate; calyx actinomorphic or zygomorphic, slightly enlarging in fruit, the lobe apices acuminate; corolla zygomorphic, 5 lobed, not bilabiate due to deeply lobed upper lip, the tube shorter or longer than calyx; stamens 4, exserted, the anther sacs slightly to strongly divaricate with none abortive; ovary sessile, lobed in upper ; stigma unevenly 2 lobed. NUTLETS: obovoid, rugose reticulate or irregularly ridged, often pubescent. x = 7, 10, 19. NOTES: 17 spp.; se Can. to Pue., Mex. (Greek.: thrix = hair and stema = stamen, referring to the thin, elongate filaments). Lewis, H. 1945. Brittonia 5:276 303. REFERENCES: Christy, Charlotte M. 2003. Lamiaceae. J. Ariz. – Nev. Acad. Sci. Volume 35(2).