New Descriptions and a New Species of Rhynchospora from Northeastern Brazil: Notes on Brazilian Cyperaceae I.

Abstract

Summary. Two little-known and one new species of Rhynchospora Vahl sect. Pseudocapitatae C.B. Cl. from northeastern Brazil are described and illustrated. Rhynchospora Vahl sect. Pseudocapitatae C.B. Cl., as recognised by Kiikenthal (1949), comprises c. 13 species all of which occur in Brazil. The main characteristics of the section are: a triangular culm subtended at the base by several leaves; an inflorescence composed of 1-several sparsely branched corymbs, with each corymb in the form of a pseudocapitulum which is often pedunculate, and an achene which is biconvex and transversely rugose. The current problem came to light while examining specimens of Cyperaceae from the state of Bahia. Amongst these were plants which had affinities with sect. Pseudocapitatae, but could not be matched with any material at Kew. Initially it appeared that the material represented two new taxa. However, among the species described in Clarke (1908), was R. ridleyi C.B. Cl. The description of this species corresponded with most of the Bahian specimens, and identification was confirmed by type material in BM. A further description was given in Kiikenthal (1949). As both descriptions of R. ridleyi were brief and based on only one plant, a more detailed account of it is given below. However the remaining specimens could not be identified, and after an extensive herbarium and literature search it was clear this material represented a new species. A name for it, together with a full description are given below. A third species, R. aberrans C.B. Cl. was also examined. Its status was similar to that of R. ridleyi, having been described only briefly in Clarke (1908) and Kiikenthal (1949). A new description is, therefore, provided. In addition a specimen was discovered in BM, which represents an isolectotype of the species.