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, Republic of: 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).
Irlbachia in Nov. Gen. Sp. Pl. 2: 101. 1827 sec. by Lena Struwe. - Irlbachia in JEANETTE ALLOGIO, LAURA COBB, JASON R. GRANT, MARION J. JANSEN-JACOBS, MATT KINKADE, KATHERINE B. LEPIS, HILTJE MAAS-VAN DE KAMER, PAUL J.M. MAAS, MATTHEW I. PALMER & S. MOTA DE OLIVEIRA, FLORA OF THE GUIANAS, Series A: Phanerogams Fascicle 30 139. GENTIANACEAE. 2012
- ≡Lisianthus (Irlbachia) in Benth. & Hook.f., Gen. Pl. 2: 814. 1876
- ≡Irlbachia (Elegans) in Mem. New York Bot. Gard. 32: 368. 1981
- =Pagaea in DC., Prodr. 9. 1845
- Type: Enicostema poeppigii
- =Lisianthus (Brachycodon) in Hooker, J. Bot. Kew Gard. Misc. 6: 200. 1854
- ≡Brachycodon in Mart., Fl. Bras. 6: 229. 1865