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Common name: 

Latin name and synonyms: Tapeinostemon Benth., Hooker's J. Bot. Kew Gard. Misc. 6: 194 (1854).
Synonym: Stahelia Jonker, Recueil Trav. Bot. Néerl. 34: 494 (1937)

Species:   Seven species.

Distribution:   Northern South America, primarily the Guayana Shield, with one outlier in the Andes (T. zamoranum).

Habitat:  This genus grow in a variety of habitats, from lowland savannas and rainforests of the Amazon Basin and Guyanas, to high-altitude areas up to 2200 m in the Andes (T. zamoranum) and the tepuis of the Guayana highlands (several species).

Characteristics:   Perennial herbs, upright and sometimes slightly woody at the base of the plant. Stems rounded (terete). Leaves petiolate, elliptic, lanceolate, to ovate. Flowers 5-merous, in lax cymes or heads (T. sessiliflorum). Calyx with relatively long lobes, without colleters. Corolla white, yellow, or orange, salver- to funnelshaped or tubular, with relatively short lobes. Stamens inserted in the middle of the corolla tube; anthers basifixed, free or fused to each other, with long sterile apices.  Pollen in monads (single pollen grains). Ovary ovoid, tapering into style, 2- or 4-celled; placentas protruding inwards; stigma bilobed.

Evolution and related plants:   Tapeinostemon is tentatively placed in tribe Saccifolieae based on its palynological and floral similarities with other genera in this tribe [Struwe et al., 2002].

Economic uses:  None known.

Notes: Tapeinostemon is one of only a few gentian genera with heterostylous flowers.  This means that some flowers of a species have a long style and shorter stamens, and other flowers have a short style and longer stamens, promoting cross-pollination. So far this character has only been seen in Tapeinostemon longiflorum [Struwe et al., 2002], but it might be present in other species as well.  Other heterostylous gentian genera are Hockinia and Voyriella. Tapeinostemon also show variation in the fusion of the anthers, with some flowers having free anthers and others having fused (connate).

Accepted/Selected species (synonyms in parenthesis) and their distribution:

References and publications: 

Steyermark, J. A. 1951. The genus Tapeinostemon (Gentianaceae). Lloydia 14: 58-64.

Struwe, L., J. W. Kadereit, J. Klackenberg, S. Nilsson, M. Thiv, K. B. von Hagen, & V. A. Albert. 2002. Systematics, character evolution, and biogeography of Gentianaceae, including a new tribal and subtribal classification. Pp. 21-309. In: L. Struwe & V. A. Albert (eds.), Gentianaceae: Systematics and Natural History, Cambridge University Press, Cambridge.

Struwe, L., P. J. M. Maas, O. Pihlar, & V. A. Albert. 1999. Gentianaceae. Pp. 474-542. In: P. E. Berry, K. Yatskievych, & B. K. Holst, editors. Flora of the Venezuelan Guayana, vol. 5. Missouri Botanical Garden, St. Louis.  (images)

© Lena Struwe, 2004