Type: Chamaecostus subsessilis
Low or very small plants, occasionally acaulescent rosettes, never exceeding 1m in height. Leaves elliptical, acuminate to long-acuminate at the apex. Inflorescence often capitate, not tightly compressed. Bracts chartaceous to herbaceous, green or green-yellow often with deltate appendages. Bracteole membranous, tubular, bicarinate adaxially. Calyx membranous, cylindrical, toothed at apex. Corolla tube exserted from the calyx; lobes large, membranous, lanceolate. Labellum large, forming a long narrow tube that opens broadly to ovate at the apex, greatly exceeding petals and bracts in length. Corolla and labellum usually of the same color, yellow or orange to white (but vibrant red in C. lanceolatus). Stamen petaloid; tip reflexed, triangular, covering the opening to the nectary chamber. Pollen grains large to very large according to Maas (1972). Ovary trilocular. Stigma cup-shaped. Fruit capsule membranaceous, tardily dehiscent. Floral parts red-brown punctate.
This genus is comprised of 8 species with a distribution restricted to South America from the Guyana shield to the Amazonian lowlands of Bolivia and Brazil at the western edge of the Brazilian shield.
Phylogeny and Classification:
Chamaecostus is sister to Dimerocostus plus Monocostus clade. Together, these three genera form an entirely New World clade at the base of the family Costaceae.
This genus is comprised of 8 species. The plants are all small in stature, which initially prompted their separation from the remaining Neotropical members of the genus Costus into the subgenus Cadalvena by Schumann. In addition, they have an open labellum that is more characteristic of Monocostus and Dimerocostus in the new world, as well as several species of African Costus and Asian Cheilocostus.
Ecology and Pollination Biology:
The pollination syndrome is open-flowered generalist, but no records are available to indicate specific pollinators.
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