Volume 83Number19962A REVISION OFDISCOCARPUS(EUPHORBIACEAE)'Annalsof theMissouriBotanicalGardenSheila M. Hayden and W. John Hayden2ABSTRACT As revised here, Discocarpus is interpreted to consist of three neotropical species: P. essequeboetnsio. Klotzsch, 1).gentryi S. M. Hayden, which is described and named herein as new lo science, and D. spruceanus Mill. Arg. Onepreviously accepted name, D. brasilien.sis Klotzsch ex Mll. Arg., is reduced to synonymy of D. essequehoensis. Iecto-types are proposed for the two species previously described. One species is newlyv excluded from Discocarputs. as arethree others, following previous literature. Foliar analomy is described with a focus on epidermal sclereids, which areshown to occur on both epidermides. Evidence presented supports close relationships with Ijichnostylis Turcz. andAmanoa Aubl.; little was found to support previous hypotheses concerning a relationship with Chonocentrum Pierre exPax & K. Hoffm. Discocarpus Klotzsch is a genus of trees found inseasonally flooded riparian habitats of northernSouth America, where they are components of theforest canopy. The plants are dioecious and bearsmall clusters of flowers in the axils of simple, al-ternate, entire leaves. Discocarpus was first described by Klotzsch(1841) who initially named, but did not describe,two species; he subsequently described one ofthese, D. essequeboensis Klotzsch (1843), based onSchomburgk collections fromn the Essequibo Riverregion of Guayana. Omitting two nettles (Urtica-ceae) from Mexico and Nicaragua grossly misplacedin the genus, the next species of Discocarpus to benarned was D. spruceanus Mull. Arg. (1863), basedon collections of Richard Spruce from the Rio Ne-gro of Brazil. Some 32 years after being first men-tioned by Klotzsch, D. brasiliensis Mill. Arg. (1873)was formally named, based on a collection of vonMartius from the early 19th century. Three taxawere added to the genus in the 20th century. Thefirst addition was D. hirtus (L. f.) Pax & K. Hoffm.(Pax & Hoffmann, 1922), a consequence of syn-onymizing the South African genus Lbchnostyliswith Discocarpus. In current literature, however,l�ichnostylis is treated as distinct from Discocarpus(e.g., Levin, 1986; Mennega, 1987: Webster,1994b). The two most recently described species. ' Financial support for the master's thesis research upon which this study is based was generously provided by theGraduate School of Arts and Sciences at the Universily of Richmond. We thank Rafael de Sa, Miles F. Johnson. GeoffreyA. Levin, Gary Radice, Dean Simpson, Donna M. E. Ware, and an anonymous reviewer for assistance, and the curatorsof BM, BR, C, E, F. G, GH, GOET, ILLS. K, L. tl), M, MANCH. MICH, MO, NY, OXF, P, R, Rh, RSA, S, TCD. [j.UC, URV, US, and W for the loan of herbariurn specimens. 2 Department of Biology, University of Richinond. Richmond. Virginia 23173, U.S.A. ANN. MissouRI BOT. GARD. 83: 153-167. 1996.�*
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