Perama is a morphologically and, to some extent, biogeographically odd genus of about a dozen species, which is found in open areas on nutrient-poor substrates in seasonal climates in South America. The plants are generally slender annuals and low perennials with small but showy flowers, and several are easily overlooked even when in flower, and are more easily overlooked as Rubiaceae. Perama is characterized by opposite to verticillate leaves sometimes with markedly subpalmate venation, stipules that are reduced to a line of glands or sometimes obsolete, terminal and axillary, subcapitate to glomerulate inflorescences with the bracts reduced to scale, distylous, small, four- or rarely five-merous flowers, calyx limbs with two or four (to five) developed, often setose lobes, white to pink or yellow corollas with the lobes vaflvate in bud, and small circumscissile capsules with one seed in each locule. Its centers of diversity are in the Rio Negro basin and east-central Brazil. The most widespread species are Perama dichotoma and Perama hirsuta. 

The growth forms of the species vary rather markedly, with the leaves borne along the stem or in basal rosettes, and the inflorescences borne on various short to well developed terminal peduncles to clustered within the leaves. Some species have verticillate leaves, which have not been studied in detail but may represent paired leaves with foliceous stipules as in Rubia. The species with opposite leaves in basal rosettes often appear verticillate unless examind carefully. Some Perama species have leaves with markedly subpalmate venation, which is unusual in Rubiaceae. In some plants the leaves are fused at their bases around the stem, which may represent a former, developmental fusion with the interpetiolar stipules that are reduced. A few species have large, lax cymose inflorescences with very slender axes; that of Perama carajasensis is particularly robust and striking.Some of the species are notable in their dense sericeous pubescence; the development of this sometimes varies within species. Individual plants of a species also often vary markedly in size in development, which is probably related at least in part to their habitat in microsites of varying humidity and nutrient concentration in seasonal habitats. 

Perama species have been variously included in Verbenaceae, because of their leaves that appear to lack stipules, and in Melastomataceae because of their subpalmate leaf venation. The classification of this genus within the Rubiaceae has also been problematic, until it was finally separated in its own tribe; Perama does not seem to have been studied with molecular phylogenetic data yet. The genus was first reviewed comprehensively by Steyermark (1963: 232-250), who detailed the morphology and noted the dimorphic distylous flowers but did not understand their biology. He recognized a number of varieties and forms, based on various features but especially development and details of the pubescence, leaf arrangement and size, and calyx lobe form. The genus was then reviewed again, with more nomenclatural detail, by Steyermark & Kirkbride (1977). They named several new specis and recognzied four taxonomic sections, three of them first distinguished by Schumann (1889), which were characterized but not keyed. Sect. Perama was characterized by yellow corollas, vs. white, pink, or blue in the other sections. Sect. Buchia has an inflorescence comprising a fascicle of odd, subsessile, terminal spikes, and leaves in a basal rosette. Sect. Rosella has a compound inflorescence, with apparenlty one or more order of branching, and basal leaves. Sect. Diperama has stems branched more or less dichotomously, as in an inflorescences, with the leaves borne along the stems at branching points. This genus has not been reviewed since their work, and the sections are provisionally not recognized here but may have merit. Most of Steyermark's infraspecific taxa were later synonymized by Taylor et al. (2004), based on review of the numerous specimens collected after his classification was published. 

Perama is similar to some Melastomataceae species, but those have free petals and stamens. Perama can be confused with some species of Limnosipanea, which is found in similar habitats but has capsules with numerous seeds. Some species of Perama in eastern Brazil are also similar to some specides of Declieuxia, with indehiscent didymous fruits. 

Author: C.M. Taylor.
The content of this web page was last revised on 5 May 2020.
Taylor web page: http://www.mobot.org/MOBOT/Research/curators/taylor.shtml

• Steyermark, J. A. 1963. Rubiaceae In: B. Maguire & collaborators, The botany of the Guayana Highland—Part V. Mem. New York Bot. Gard. 10(5): 186–278.
• Steyermark, J. A. & J. J. H. Kirkbride. 1977. Review of the genus Perama (Rubiaceae). Brittonia 29(2): 191–198.
• 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.