Small annual herbs. Stems erect or prostrate, obscurely to distinctly quardangular. Leaves opposite, simple, sessile, 3–5-palmately nerved. Flowers small, solitary and axillary, terminal raceme or terminal and axillary racemes. Calyx deeply 5-lobed. Corolla tubular, bilabiate; upper lip either entire or emarginated to shallowly 2-lobed, lower lip usually widely spreading 3-lobed, upper lip usually shorter than lower lip. Stamens 2 or 4, didynamous; posterior stamens usually fertile and affixed to corolla tube, anterior stamens fertile or reduced to staminodes, bilobed, ; usually anterior filaments each with distinct spur arising at or near the base; anthers free or contiguous, thecae divaricate; cleistogamous flowers often present in L. procumbens. Ovary superior, subglobose to ellipsoid, glabrous, bicarpelate with 2 locules, axial placenta with numerous ovules; style slender, erect; stigma bilamellate, flat. Fruits septicidal 2-valved capsules, ellipsoid or turbinate, somewhat or subglobose. Seeds numerous, longitudinal furrows (aulacospermous) with reticulate ridges, variously shaped.