Argostemma (PROSEA)
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Introduction |
Argostemma Wallich
- Protologue: Roxb., Fl. ind. 2: 324 (1824).
- Family: Rubiaceae
- Chromosome number: x= 11
Origin and geographic distribution
Argostemma is a large, complex palaeotropical genus with about 220 described species, but the actual number of species is probably approximately 100. Peninsular Malaysia and Borneo are rich in species (about 30 each), whereas Java has only 5 species. Only two species occur outside tropical Asia, both in West Africa.
Uses
There are some records on the use of Argostemma roots and leaves to treat fever, both externally and internally.
Botany
Creeping to erect herbs, often succulent; stem usually unbranched or slightly branched, with short internodes. Leaves opposite or sometimes verticillate, those of a pair or verticel often unequal, sometimes rosulate; petiole short or absent; stipules interpetiolar. Inflorescence usually terminal, cymose, corymbiform to umbelliform. Flowers bisexual, 4-5(-6)-merous, regular (rarely zygomorphous); calyx with a very short tube, lobes succulent in fruit; corolla gamopetalous, rotate or subcampanulate, white, often with greenish spots at base, lobes usually much longer than tube; stamens inserted near the base of the corolla tube, filaments free, anthers coherent into an anther tube, longitudinally dehiscent, or sometimes free (then opening by apical pores); ovary inferior, 2-celled, style filiform. Fruit a succulent capsule crowned with limb of calyx, opening by an apical operculum, many-seeded. Seeds minute, angular or ovoid, usually with reticulate testa.
The flowers are very characteristic: bright white and often Solanum -like because of the large, fused anthers and corolla often with short tube and reflexed lobes. This flower type is widespread in both dicotyledons and monocotyledons, and adapted to insect pollination. The powdery pollen is released in small portions by vibrating movements of visiting insects, which dust their bodies. Argostemma belongs to the tribe Argostemmateae , together with the small genus Neurocalyx which is endemic to Sri Lanka and southern India.
Ecology
Argostemma is mostly found in damp, shady locations in lowland to lower montane forest.
Genetic resources
Many Argostemma species are endemic to restricted areas and consequently they seem easily liable to genetic erosion or even extinction.
Prospects
Research on phytochemistry and pharmacological properties of Argostemma is needed to judge whether the use in traditional medicine has some scientific basis. A taxonomic revision of the genus is lacking. Recent surveys of the species in Borneo and Thailand (incomplete) are available, but for other regions in South-East Asia one has to rely on old publications.
Literature
111, 757, 886.
Selection of species
Authors
R.H.M.J. Lemmens
