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This page is maintained 
by Dr. Lena Struwe 
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updated: 01/19/11 

Chorisepalum
(Gentianaceae: Helieae: Chorisepalum)

more images

 
Common name: 

Latin name and synonyms:  Chorisepalum Gleason and Wodehouse, Bull. Torrey Bot. Club 58: 451 (1931)

Etymology: After chori- (Greek for separated) and sepals, indicating the free sepals.  Sepalum is not true Latin or Greek, but a word only used in Botanical Latin, and a fusion of the Latin word separare (to separate) and the Greek word petalon (petal, leaf) [Corneliuson, 1997]. The meaning of Chorisepalum would therefore be 'separated sepal".

Species: Five species.

Distribution: All five species of Chorisepalum are endemics of the tepuis, the table-top mountains of southern Venezuela, Guyana, and Suriname.

Habitat: Grasslands and open, rocky areas on tepui summits (high-altitude)

Characteristics: Shrubs or small trees. Leaves ovate to elliptic, glossy and smooth or deeply veined and rugose. Inflorescences terminal, few-flowered, cymose, with leaf-like bracts. Flowers erect, actinomorphic. Sepals 4, not fused, leathery, lanceolate with acute apices. Corolla 6-merous, salver- to funnel-shaped, thin, green, with spreading lobes. Stamens 6, inserted in the corolla tube; filaments of equal length. Anthers linear, erect. Pollen released as monads (=single pollen grains) with reticulate exine. Gynoecium with a nectary disk around the base; style long, slender; stigma bilamellate. Capsules erect, opening up in 4 valves, eventually falling off. Seeds many, flattened and winged.

Evolution and related plants:  Chorisepalum belongs to the tribe Helieae, and is a member of the Macrocarpaea clade together with Macrocarpaea, Tachia, and probably Zonanthus.  These four genera are the only ones in Helieae with single pollen grains; all other genera have pollen grains dispersed either as tetrads or polyads. The reticulate single pollen grains of Chorisepalum are similar to Zonanthus and some Macrocarpaea and Tachia species. 

Economic uses:  None known.

Notes: This is the only genus in the gentians with a 4-merous calyx and a 6-merous corolla and 6 stamens. Other supermerous corolla genera occur in Anthocleista (10-16 corolla lobes), Prepusa (6), Potalia (8-10), Sabatia (some species up to 10 lobes), and Urogentias (8).

Accepted species (synonyms in parenthesis) and their distribution:

Chorisepalum carnosum Ewan Guyana, Venezuela
Chorisepalum ovatum Gleason Venezuela
Chorisepalum psychotrioides Ewan (Chorisepalum acuminatum Steyerm.; Chorisepalum psychotrioides var. acuminatum (Steyerm.) Maguire) Guyana, Venezuela
Chorisepalum rotundifolium Ewan Guyana, Venezuela

Chorisepalum sipapoanum (Maguire) Struwe & V. Albert
(Chorisepalum ovatum var. sipapoanum Maguire)

Suriname, Venezuela

 

References and publications

Ewan, J. 1947. A revision of Chorisepalum, an endemic genus of Venezuelan Gentianaceae. J. Wash. Acad. Sciences 37: 392-396.

Maguire, B. 1981. Gentianaceae. Pp. 330-388. In: B. Maguire & collaborators, editors. The Botany of the Guayana Highland Part XI. Mem. New York Bot. Gard. 32.

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

 

Gentian Research Network, 2002-2011.
For corrections and additions, contact Lena Struwe at struwe@aesop.rutgers.edu