Description from Flora of China
Herbs [rarely small shrubs or cushion plants], annual [or perennial], bearing glandular [and/or non-glandular] trichomes [seldom completely glabrous]. Leaves cauline or in a basal rosette [rarely whorled or imbricate]. Inflorescences lax spikes, cymes [racemes, panicles, pseudoheads, or corymbs], or with flowers solitary. Flowers perfect, zygomorphic. Calyx lobes 5, [distinct or] with 3 distinct and 2 connate [occasionally 2-labiate]. Corolla 5-merous, irregular; throat appendages (paracorolla) often present; lobes 5 but lowest (labellum) much smaller, usually reflexed, simple [or appendiculate]. Gynostemium usually exserted from corolla, bent and irritable [rarely erect and immobile]; anthers 2-locular; stigma entire [or 2-cleft]. Ovary incompletely 2-locular [or 1-locular due to reduction of septum]; ovules few to more often numerous.
Almost all species occur in Australia with Asia only having seven species, six of which are endemic to Asia.
About 300 species: tropical Asia, Australia, New Zealand; two species in China.