Recent plant collecting and exploration in Palawan, Philippines, led to the rediscovery of a Microrphium (Gentianaceae) species that had not been validly published. The Palawan species, M. elmerianum, extends the distribution range of the genus, which is known previously from the Malay Peninsula and Thailand. The biogeographic significance of this finding, as well as its significance to the conservation needs of Palawan's unique plant diversity, are briefly discussed. Recent plant collecting and exploration of the island of Palawan in the Philippines have contributed substantially to advancing our botanical and biogeographic knowledge of the flora of this island (Podzorski, 1985; Regalado et al., 1995; Soejarto et al., 1989, 1996b). The last period of exploration was conducted from 1987 to this date: on the one hand by the University of Illinois at Chicago, under the auspices of the United States National Cancer Institute, as part of an anticancer and anti-AIDS plant screening program (Soejarto, 1993; Soejarto, 1995; Soejarto et al., 1996a) with the cooperation of the Philippine National Herbarium, Manila (PNH), and on the other, by the Philippine Plant Inventory Project, funded by the U.S. National Science Foundation (Stone, 1991). One interesting botanical rediscovery was a member of the gentian genus Microrphium on this island. A specimen belonging to this taxon was first collected in 1911 by an American botanist, A. D. E. Elmer, along Iwahig River and was not described until 1939. Elmer named it Microrphium palawanense and described the plant in English (Elmer, 1939). He did not provide a Latin description nor a diagnosis, hence the name is rendered invalid according to Article 36 of the International Code of Botanical Nomenclature (Greuter et al., 1994). The designated type specimen, Elmer 12923 (holotype, PNH+), was distributed under the name of Lysimachia (Elmer, 1939). Duplicates of this specimen could not be found in spite of efforts of the first author (JCR) to locate them in major herbaria (A, F, GH, NY, US) where Elmer may have sent the duplicates. Merrill (1923) referred to the specimen Elmer 12923 as representing an undescribed species of the genus; the only other species of the genus was previously known from the Malay Peninsula. Two collecting expeditions in Palawan by the second author (DDS) yielded specimens that match Elmer's species from the description. This discovery enabled us to describe Elmer's species with the requirements for valid publication. Microrphium elmerianum Regalado & Soejarto, sp. nov. TYPE: Philippines. Palawan Island: Municipality of Puerto Princesa, Bacungan hills and slopes above Nagtabon beach, 9051'N, 118037'E, 50-100 m, 9 Apr. 1989, Soejarto, Reynoso, Sagcal, Rutz & Edrada 6499 (holotype, F #2027197; isotypes, A, PNH). Figure 1. Species Microrphio pubescenti C. B. Clarke affinis sed pubescentiis ochraceis haud cinereis, foliis sessilibus, inflorescentiis glabris differt. Erect herb up to 60 cm tall. Stems terete, smooth, 5 mm diam.; branches apically yellowish brown puberulent, becoming glabrate toward the base. Leaves opposite, well scattered along the stem, subcoriaceous, sessile, elliptic, 5.5-6.5 cm long, 2.5-3.0 cm wide; apices obtuse to obtusely rounded; bases cuneate-attenuate, clasping the nodes, leaving annular scars after falling; margins entire and minutely ciliate; nerves 3 pairs, obliquely ascending, brown-puberulent beneath, reticulations absent; surfaces glabrate above, finely pubescent below. Inflorescences many-flowered, paniculiform cymes (thyrses), glabrous; rachises slender, terete, up to 30 cm long; floral bracts foliaceous, ovate, 10-20 mm long, 5-10 mm wide, paired, connate at the bases; bracteoles foliaceous, elliptic, 3-4 mm long, 2-3 mm wide, stiffly subtending each flower at the base of slender, terete pedicels 3-4 mm long. Flowers white; calyx ellipsoid, 5 mm long, 3 mm wide, glabrous, 2-lipped with wide slits on opposite sides down to the midNovoN 7: 77-80. 1997. This content downloaded from 40.77.167.54 on Sun, 15 May 2016 06:20:27 UTC All use subject to http://about.jstor.org/terms