Notes on Osmoxylon (Araliaceae), II

The mainly East Malesian araliaceous trees and shrubs characterized by inflorescences with ‘false fruits’ were first accorded generic rank by Miquel (1863) under the name Osmoxylon. The name stood for the elegance of the vegetative parts of the plants as depicted by Rumphius and once collected by Zippelius. In the next decade, working partly from his own collections and emphasizing the distinctive inflorescences and their biology, Beccari (1878) added several species with palmately lobed or dissected leaves and described the characteristic reproductive mechanism. In a further study, however, Boerlage (1887) separated the palmately veined species as Eschweileria. This latter name was a homonym and Harms (1894) not unnaturally proposed Boerlagiodendron. Eighty years later, revision for Flora Malesiana brought about a reassessment and, as some species appeared to be ‘intermediate’ (notably B. dinagatense Merr. and B. simplicifolium Elmer, respectively from Dinagat Island and NE Mindanao in the Philippines) the two genera were merged by Philipson (1976, 1979) without recognition of any formal subdivisions. Further study indicates, however, that the former Boerlagiodendron and Osmoxylon s.s. do form distinct groups. Osmoxylon dinagatense (Merr.) Philipson and O. simplicifolium (Elmer) Philipson may have simple leaves, but both have – though rather small – a typical erect ‘Boerlagiodendron’ inflorescence. In O. simplicifolium, based on Elmer 13689 from NE Mindanao (Philippines), the leaves are coarsely toothed and feature craspedodromous venation. There is a further record from Samar [PNH 117163 (Gutierrez et al.) Osmoxylon dinagatense, based on BS 35220 (Ramos & Pascasio) from Dinagat Island, is similar but the leaf apex is more obtuse and the margins are merely crenate, the teeth obscure. I interpret these species as representative of miniaturization, a process also evident within O. micranthum (Harms) Philipson. Little is known of their ecology; however, Dinagat is known to have serpentine surface rock and in Samar the collection of O. simplicifolium was recorded from forest on limestone. Both species are shrubs or small trees to 4 m. With respect to O. oblongifolium Philipson (no. 8 in Philipson, 1979), also described as having simple leaves, its author has noted that the petiolar crests are sometimes fimbriate and the leaf-blades occasionally have a small triangular lobe on each side below the middle. The plants are moreover stream-bank dwellers and the leaves are clustered at branch ends. All these indicate membership of the Boerlagiodendron group.