Annual or perennial herbs, erect, prostrate, creeping to ascending. Stem usually quadrangular, winged or terete. Leaves exstipulate, simple, opposite, petiolate; leaf blade margin toothed or serrate or entire. Inflorescence mostly axillary or terminal spikes or terminal raceme or cyme or flower solitary axillary. Bracts and bracteoles small and linear. Flowers bisexual, zygomorphic, hypogynous, bilabiate, pink or pale purple. Calyx bilabiate, tubular, persistent, lobes 5, unequal. Corolla tubular or cylindric, 5-lobed, bilabiate, lower lip larger, of 3 imbricate lobes, upper lip smaller, 2-lobed. Stamens usually 4, didynamous, anterior 2 longer inserted in corolla tube, included or slightly exserted; anthers bithecous, longitudinal dehiscence. Carpels 2, syncarpous; ovary superior, usually unilocular (rarely 2-locular), ovule solitary, nearly erect from base; style terminal; stigma broadly 2-lobed. Fruit caryopsis (achene), loculicidal capsule or occasionally berry-like with membranous pericarp, enclosed by persistent, ribbed, reflexed, 3-hooked calyx; fruit rarely capsular with many seeds. Seeds numerous, rarely to 1.

15 genera and about 205 species

Mimulus hybrid