Cochliostema is a small genus of flowering plants in the spiderwort and dayflower family (Commelinaceae), order Commelinales. It contains two species native to the Neotropics, ranging from southern Nicaragua to southern Ecuador. The genus belongs to the subtribe Dichorisandrinae within the tribe Tradescantieae; its closest relatives are Plowmanianthus and Geogenanthus, with which it shares the distinctive feature of flower petals fringed with moniliform trichomes.
Plants are rosette-forming, typically unbranched herbs with somewhat succulent, strap-shaped leaves. In the wild, they grow primarily as epiphytes, though terrestrial individuals are occasionally found on or around tree falls, suggesting prior epiphytic growth. Cochliostema odoratissimum, the larger of the two species, is a tank-epiphyte that collects water in its leaf bases, resembling certain bromeliads in this respect. Its leaves can reach one meter in length, with plants sometimes attaining two meters in height.
The flowers are borne in large thyrses and are among the largest in the Commelinaceae, reaching approximately 2.5 centimeters in diameter. They are notably fragrant and structurally complex. Each flower has three sepals, three blue to blue-violet fringed petals, three stamens fused by their filaments in the upper half, and three carpels fused into a single trilocular pistil. The fused staminal structure bears three spirally coiled anthers enveloped and concealed by petaloid extensions, called cuculli, of the lateral stamen filaments; these narrow into two distal hose-like extensions. This distinctive coiled anther morphology gives the genus its name, from Greek roots meaning "spiral male parts."
The two recognized species are Cochliostema odoratissimum Lemaire and Cochliostema velutinum R.W.Read. A 19th-century name, C. jacobianum, still encountered in horticulture, is now considered synonymous with C. odoratissimum.
Etymology
The genus name Cochliostema derives from Greek kochlias ("snail" or "spiral") and stema ("stamen"), meaning "spiral male parts." It refers to the distinctive spirally coiled anthers that characterize the flowers. The 20th-century botanist William T. Stearn spelled the name as Cochleostema.
Distribution
Cochliostema occurs in the Neotropics, with its range extending from southern Nicaragua through Central America to southern Ecuador. Both species are found within this region.
Ecology
Cochliostema species are predominantly epiphytic herbs that grow on trees in humid tropical forests. Cochliostema odoratissimum is a tank-epiphyte, forming a water-holding rosette of leaf bases that collects rainwater and organic debris, a growth habit convergent with that of many bromeliads. Terrestrial individuals are occasionally encountered on or around fallen trees, suggesting they began life as epiphytes before their host tree collapsed.
Taxonomy
Cochliostema is placed in the subtribe Dichorisandrinae of the tribe Tradescantieae within Commelinaceae. Its closest relative is Plowmanianthus, followed by Geogenanthus; all three genera share flower petals fringed with moniliform (bead-like) trichomes, a synapomorphy for the group. The two recognized species are C. odoratissimum Lemaire and C. velutinum R.W.Read. The name C. jacobianum, described in the 19th century and still used in horticulture, is a synonym of C. odoratissimum.
