Chalepophyllum is a genus with one species of low shrubs found in cloud forest scrub vegetation in the tepuis of the Guayana Highlands, in northeastern South America. These plants are characterized by their branched shrub habit; tissues without raphides; interpetiolar triangular stipules that are persistent; rather small, rounded to obovate leaves that are leathery and subsessile; axillary inflorescences composed of a pedunculate flower or a shortly cymose group of 2-5 or so flowers; homostylous 5-merous flowers; deeply lobed calyx limbs; funnelform to salverform white corollas that are barbate in the throat and have convolute lobes; and small woody ellipsoid capsules that are septicidally dehiscent and contain numerous small, angled to shortly winged seeds. The name of the type species was spelled in the original publication as "guyanense", but later authors often used a different spelling, "guianense"; the first spelling is the correct one. This species was illustrated well by Steyermark (1974: 324, fig. 52)

Chalepophyllum is rather variable morphologically in the size and degree of lobing of both the corolla and the calyx, as well as in leaf size, length of the petioles, and capsule size. When few collections were available this variation seemed to mark separate taxa, and Steyermark therefore recognized two species and two varieties of Chaleophyllum guyanense. He separated these species by the relative length of the corolla lobes to the corolla tube, and the varieties by leaf shape. However with more collections now available, the variation does not seem correlated with any geographic region and the individual characters are not correlated with each other, so these plants are currently best regarded as a single species. Such morphological variation is not unknown in Rubiaceae species that grow in seasonal and/or fragmented environments, but in this case it may eventually deserve more detailed study. In addition to the variation in size of the calyx lobes that is found among different plants, the calyx lobes also often enlarge markedly on an individual flower as the fruits mature.

Chalepophyllum was confused at one time with Maguireothamnus, which is found in the same region and has a similar habit and also has capsular fruits. However Maguireothamnus can be separated by its much larger corollas with well developed slender tubes and its larger capsules with loculicidal dehiscence. Chalepophyllum is also similar to Duidania, which is found in the same region as these other two genera. Duidania differs from Chalepophyllum in its terminal multiflowered inflorescences, capsules with loculicidal dehiscence, and flattened winged seeds. Chalepophyllum is also similar to Dendrosipanea revoluta, which has elliptic petiolate leaves and terminal inflorescences. Chalepophyllum is also similar to Neblinathamnus, with dull red corollas, loculicidal capsules, and unwinged seeds. 

Author: C.M. Taylor.
The content of this web page was last revised on 15 September 2020.
Taylor web page: http://www.mobot.org/MOBOT/Research/curators/taylor.shtml

• Taylor, C. M., J. A. Steyermark, P. G. Delprete, A. Vincentini, R. Cortés-Ballén, D. C. Zappi, C. H. Persson, C. B. Costa & E. Anunciação. 2004. Rubiaceae. 8: 497–847. In J. A. Steyermark, P. E. Berry & B. K. Holst (eds.) Fl. Venez. Guayana. Missouri Botanical Garden Press, St. Louis.
• Steyermark, J. A. 1974. Rubiaceae. 9(1): 7–593. In T. Lasser (ed.) Fl. Venezuela. Fondo Editorial Acta Científica Venezolana, Caracas.