A taxonomic revision of Dichelachne Endl. (Gramineae) with some new combinations in Stipa L. and Oryzopsis Michx

Dichelachne was established by Endlicher in 1833 to accomodate a species collected by Ferd. Bauer in Norfolk I. Trinius and Ruprccht (1843) revised the genus, adding 6 more species, referring to previously published names, but giving new names as they had no access to the type materials of these. It has appeared that their specific concept was too narrow and in current literature only 4 species are accepted. This number has been reduced here to 3. Some other species have been placed in this genus now and then, but have proved to belong to different genera, as Deyeuxia, Agrostis, Stipa, and Oryzopsis. This shifting of species between quite different genera reflects the instability of the opinion about the taxonomic place of the genus. Some, as Trinius (1836), Trinius & Ruprecht (1843), F. v. Mueller (1873), and Pilger (1954) have considered it as a Stipea, others such as R. Brown (1810), Bentham (1878), Bentham & Hooker f. (1883), C. E. Hubbard (1934), and Miss Vickery (1961) have regarded it as an Agrostidea. Terrell (1971) placed it, together with Agrostis and Calamagrostis, in the Aveneae because of the presence of liquid endosperm. Although there is an overall resemblance to Stipa, closer inspection shows that it is very closely related to Deyeuxia of the Agrostideae in view of the dorsal, unarticulated, and simple awn, the microscopic, but sometimes well-developed rachilla-process which in Dichelachne crinita sometimes bears up to 3 florets, and the punctiform hilum. The difference with Deyeuxia is very slight, and mainly regards the lenght of the awn and the callus-hairs, as may be observed from the table.