A taxonomic revision of southern hemisphere bracteate-prostrate forget-me-nots (Myosotis L., Boraginaceae) is presented here. The group comprises mostly species endemic to New Zealand plus the South American Myosotis antarctica Hook.f. (also Campbell Island) and M. albiflora Hook.f. The statistical analyses of morphological data from herbarium specimens reported here support recognition of five main subgroups on the basis of habit. Excluding the M. pygmaea Colenso species group (M. antarctica, M. brevis de Lange & Barkla, M. drucei (L.B.Moore) de Lange & Barkla, M. glauca (G.Simpson & J.S.Thomson) de Lange & Barkla, and M. pygmaea), which is being treated elsewhere, 14 species are recognised in the following four remaining subgroups: (1) creeping-species group: M. matthewsii L.B.Moore, M. chaffeyorum Lehnebach, M. spatulata G.Forst., M. tenericaulis Petrie, and M. albiflora; (2) cushion-species group: M. uniflora Hook.f., M. pulvinaris Hook.f., and M. glabrescens L.B.Moore; (3) M. cheesemanii + M. colensoi species group: M. cheesemanii Petrie and M. colensoi J.F.Macbr.; and (4) M. lyallii species group: M. lyallii Hook.f. and new species M. retrorsa Meudt, Prebble & Hindmarsh-Walls. New species Myosotis umbrosa Meudt, Prebble & Thorsen and M. bryonoma Meudt, Prebble & Thorsen do not fit comfortably within these subgroups. Myosotis elderi L.B.Moore is treated as M. lyallii subsp. elderi (L.B.Moore) Meudt & Prebble. For each of the 14 species revised here, a key to species, descriptions, phenology, distributions, maps, illustrations, specimens examined and notes are provided. Some specimens examined do not fit within these species and require additional comparative studies, including with certain ebracteate-erect species, before taxonomic decisions can be made. Future research on these and other southern hemisphere Myosotis should incorporate the morphological data presented here, with additional genetic, cytological, pollen, and other data in an integrative systematic framework.
