Nomenclatural problems in Pleurozia (Pleuroziaceae):: the lectotypification of Pleurozia Dumort., Jungermannia sphagnoides Schwagr, Pleurozia sphagnoides Dumort., P-purpurea Lindb., Mnium jungermannia L. and Jungermannia undulata L. (Hepaticae)

A review is presented of nomenclatural problems in the genus Pleurozia Dumort. including the typification of five binomials relevant to the study of the genus. It is shown that the first lectotypification of Pleurozia by P sphagnoides Dumort. 1874 can be maintained and that this preserves traditional usage of Pleurozia. The earlier Jungermannia sphagnoides Schw5gr. 1814 is shown to be nomenclaturally independent and is newly lectotypified confinning its application to a species of the unrelated genus Schistochila. A new lectotype for Pleurozia purpurea Lindb. 1877 was found necessary, and this is designated from the previously overlooked herbarium of John Lightfoot (K). Mnium jungermannia L. is a heterogeneous element, in the past considered by some to include Pleurozia purpurea; it is lectotypified by a Dillenian illustration, supported by an epitype from Dillenius's herbarium that belongs to Scapania undulata (L.) Dumort. Mnium jungermannia and all names based on it, none of which are in current use, therefore become synonyms of S. undulata. Jungermannia undulata L. [equivalent to Scapania undulata (L.) Dumort.], also typified by a Dillenian illustration, is further stabilised in its current application by designation of an epitype in Dillenius's herbarium.