Description: Herbs or undershrubs; branches 4-angled.
Leaves toothed or finely crenate to ± entire.
Inflorescences terminal, with 4–6 flowers per node; internodes elongate basally. Calyx tubular campanulate, 10-veined, 2-lipped; lower lip 4-toothed, with lateral lobes oblong and aristate, median lobe subulate; upper lip broad, membranous, often recurved, strongly decurrent. Corolla 2-lipped; tube slender; lower lip entire, concave; upper lip 3- or 4-lobed. Stamens 4, fertile, included or greatly exserted from corolla tube; anther loculi confluent. Ovary 4-lobed; style gynobasic; stigma capitate or clavate.
Distribution and occurrence: World: c. 40 species, chiefly tropical regions of Africa & Asia to Australia. Australia: 1 species (native).
Text by B. J. Conn