Herbs. Leaves sessile or petiolate, 1-15 cm long; 1-5-veined. Inflorescences terminal, dichasial cyme with usually monochasial branches; bracts and bracteoles scale- or leaf-like. Flowers sessile or pedicillate, 5-merous, actinomorphic or slightly zygomorphic; calyx fused from base for ca. 1/5-1/2 of length, coriaceous, campanulate, calyx lobes elliptic, thickened and glandular dorsally, rarely with small keel, apex obtuse to acute; corolla fused at base for ca. 1/2-2/3 of length, salver- or funnel-shaped, 4-33 mm long; corolla bud apex rounded, androecium zygomorphic with stamens and style bent towards bottom of corolla mouth; stamens inserted in lower to middle part of corolla tube, of equal or unequal length, base of filaments without appendages, anthers oblong to linear, connective apex apiculate; pollen in polyads; pistil with nectary disk around base, stigma bilamellate. Fruit a capsule, with persistent calyx and persistent to late-deciduous corolla; seeds to globose, testa cupuliform and/or concave.
Guayana Highlands on tepuis present, Guyana present, N Brazil present, SE Colombia present, lowland savannas in S Venezuela present
A genus with about 9 species in total, main distribution in the Guayana Highlands on tepuis or lowland savannas in S Venezuela, N Brazil, and SE Colombia; 2 species in Guyana.
Irlbachia is here circumscribed following Maguire (1981) and Struwe et al. (2004). A larger circumscription including species of Chelonanthus, Calolisianthus, Helia, Rogersonanthus, and Tetrapollinia has earlier been advocated by Maas (1985; cf. Struwe & Albert, 1998, 1999), but is not supported by more recent phylogenetic results using molecular, morphological, and anatomical data (Struwe et al., 2004, 2008).