Preliminary remarks on Orthodontium in Europe

Abstract

The recent discovery of an Orthodontium form in two localities in Holland led us to a revision of the species concerned, viz. the species published for Europe and the type-species of the genus, O. lineare Schwaegr. It has been shown that O. gracile var. heterocarpum Wats. agrees in nearly all characters with O. lineare. Consequently the name of the variety is regarded as synonym of the type-species. O. germanicum F. W. & K. Koppe also appears to belong here. O. gracile Schwaegr. ex Br. & Schimp., however, is distinct in some important characters and is retained as a separate species. The French O. Gaumei Allorge & Thériot is markedly distinct from the other European species but is closely related to the Asiatic O. infractum. The distribution of the three species is discussed.