Bulbophyllum involutum, a new orchid species from the campos rupestres of Brazil, is described and illustrated, with notes about the biology of the species. It is also compared with B. warmningianum, B. ipanemense, and B. longispicatum. Bulbophyllum Thouars is one of the largest orchid genera, with over 1100 species, and has a pantropical distribution, concentrated especially in the Old World Tropics (Dressler, 1993). The last revision of this genus for Brazil was that of Cogniaux (1902); many species have been described more recently in various publications. At present, 54 Bulbophyllum species are recorded for this country (Pabst & Dungs, 1975, 1977). The lack of a recent revision has led to difficulty in identification of the Brazilian species and has frequently given rise to wrong determinations. One of the major taxonomic problems in this genus involves a group of species mainly found in the Brazilian campos rupestres, where about eight of these species are vegetatively uniform, and separation is only possible by use of very subtle floral characters that are difficult to recognize in herbarium material, in spite of relatively easy diagnosis in the field. These problems, in addition to the lack of a revision of the genus, have led to misinterpretations of some species, many of them being wrongly identified as Bulbophyllum warmningianum Cogniaux. In the course of reproductive biology studies of some species of this complex (Borba & Semir, in press), several populations originally interpreted as B. warmingianum and B. ipanemensis Hoehne were seen to possess some traits that separate them as a distinct species, described as follows: Bulbophyllum involutum Borba, Semir & F. Barros, sp. nov. TYPE: Brazil. Minas Gerais: Sao Gongalo do Rio Abaixo, Estagno de Pesquisa e Desenvolvimento Ambiental de Peti, 24 Apr. 1993 (fl, fr), E. L. Borba 008 (holotype, BHCB). Figures 1, 2. Bulbophyllo warmingiano Cogniaux, B. longispicato Cogniaux et B. ipanemensi Hoehne affinis, sed anthesi flore singulari, scapi bracteis floralibus purpureis, floribus purpureis majoribus, petalis ovatis, apice obtuso vel rotundato, basi labelli lobo terminale truncato vel subcordato cum margine involuto differt. Lithophytic or occasionally epiphytic herbs. Roots thread-like, fasciculate, long. Rhizome 2051 mm long between pseudobulbs, 3-6 mm diam., repent, covered with paleaceous sheaths. Pseudobulbs 19-41 x 12-22 mm, erect, ovoid, tetragonous, yellowish, monophyllous. Leaves 31-115 x 16-31 mm, sessile, erect-patent, rigid, coriaceous to slightly fleshy, elliptic-oblong to oblong, green, apex acute-apiculate, base attenuate and canaliculate. Inflorescence basal; scape 29-48 cm long, 2-3 mm diam., erect, rigid, purple, with 6-11 sheath-like bracts, 14-18 mm long, purple, later becoming paleaceous, apex obtuse; raceme 11-38 cm long, 11-30-flowered, loose, rachis purple, curv d to horizontal. Floral bracts 7.5-10.5 X 34.5 mm, ovate, persistent, purple when young and paleaceous at anthesis, apex obtuse. Flowers resupinate by torsion of the pedicel. Ovary with pedicel 4-8 mm long, obconical, purple, sulcate. Sepals coriaceous, ovate-triangular, concave, boat-shaped, acuminate, dorsal face purple, ventral face green with purple spots and points; dorsal sepal 9.6-12.4 X 3.6-4.4 mm, erect; lateral sepals 10.4-11.3 x 3.8-4.9 mm, patent to reflexed, oblique. Petals 3.35.1 x 2-3.1 mm, membranaceous, oblique ovate, patent, purple with green spots, apex obtuse to rounded, margin ciliate. Labellum 5.3-8.1 x 2.73.9 mm, fleshy, in 450 angle with the column, articulated with the column foot; lateral lobes erect, ear-shaped, ciliate, dark purple with white spots; mid-lobe purple with white apex, concave, base truncate to cordate, apex rounded, lateral margins involute, ciliate; callus dark purple, oblong, proximal half longitudinally sulcate. Column 2.4-3.8 mm long, white with purple spots, with two long, NovoN 8: 225-229. 1998. This content downloaded from 157.55.39.35 on Wed, 31 Aug 2016 04:42:35 UTC All use subject to http://about.jstor.org/terms