Osmunda, the
type genus of the
fern order,
Osmundales has historically been the largest genus in the family
Osmundaceae. Smith et al. (2006), who carried out the first higher-level
pteridophyte classification published in the
molecular phylogenetic era, described three genera in that family, namely
Osmunda,
Leptopteris, and
Todea. The genus has also been treated historically as consisting of a number of subgroups, generally subgenera,
Osmunda (3 species),
Osmundastrum (2 species), and
Plenasium (3–4 species). However, there was suspicion that the genus was not
monophyletic. The publication of a detailed
phylogeny of the family by Metzgar et al. in 2008 showed that
Osmunda as
circumscribed was
paraphyletic and that
Osmunda cinnamomea, despite its morphological similarity to
Osmunda claytoniana, was
sister to the rest of the family, and resurrected the
segregate genus
Osmundastrum, by elevating it from subgenus, to contain it and render
Osmunda monophyletic. The phylogeny of
Osmunda is shown in the following cladograms. A number of authors have proposed elevating the subgenera to separate genus level, In 2016 the Pteridophyte Phylogeny Group (PPG) classification split
Osmunda further by elevating its subgenera to genera as
Claytosmunda and
Plenasium, leaving only the species originally included in subgenus
Osmunda. •
O. abyssinica (Kuhn 1879) Bobrov •
O. acuta (Burm.fil. 1768) Fraser-Jenk. •
O. chengii Bomfleur, Grimm & McLoughlin [
Osmunda claytoniites Phipps, Taylor & Taylor non Graham 1963] •
O. herbacea Copeland •
O. hybrida Tsutsumi et al. •
O. × intermedia {
O. lancea ×
O. japonica} •
O. japonica Thunberg (Japanese flowering fern) •
O. lancea Thunberg (Japanese lancea flowering fern) •
O. x mildei {
O. angustifolia ×
O. japonica} •
O. piresii Brade 1965 •
O. regalis L. (Old World royal fern) •
O. × ruggii {
O. claytoniana ×
O. spectabilis} •
O. spectabilis Willdenow (American royal fern) •
O. wehrii Miller (Middle Miocene, Washington state)
Etymology The derivation of the genus name is uncertain. A common theory is that
Osmunda derives from
Osmunder, a Saxon name for the god
Thor. Other explanations propose that it is from
Middle English and
Middle French words for a type of fern, or mention an English folk tale of a boatman named Osmund hiding his wife and children in a patch of royal fern during the Danish invasion. ==Ecology==