Osmunda regalis

Osmunda regalis, or royal fern, is a species of deciduous fern, native to Europe, Africa and Asia, growing in woodland bogs and on the banks of streams. The species is sometimes known as flowering fern due to the appearance of its fertile fronds. The name Osmunda possibly derives from Osmunder, a Saxon name for the god Thor. The name "royal fern" derives from its being one of the largest and most imposing European ferns. The name has been qualified as "old world royal fern" in some American literature to distinguish it from the closely related American royal fern, O. spectabilis. However this terminology is not found in British literature. Osmunda regalis produces separate fertile and sterile fronds. The sterile fronds are spreading, tall and broad, bipinnate, with 7–9 pairs of pinnae up to long, each pinna with 7–13 pairs of pinnules long and broad. The fertile fronds are erect and shorter, tall, usually with 2–3 pairs of sterile pinnae at the base, and 7–14 pairs of fertile pinnae above bearing the densely clustered sporangia. In many areas, O. regalis has become rare as a result of wetland drainage for agriculture. The oldest known fossils of Osmunda date to the Paleocene, Osmunda likely derives from fossil species currently assigned to Claytosmunda. There are three to four varieties as traditionally construed: Osmunda regalis var. regalis. Europe, Africa, southwest Asia. Sterile fronds to 160 cm tall. Osmunda regalis var. panigrahiana R.D.Dixit. Southern Asia (India). Osmunda regalis var. brasiliensis (Hook. & Grev.) Pic. Serm. Tropical regions of Central and South America; treated as a synonym of var. spectabilis by some authors. Osmunda regalis var. spectabilis (Willdenow) A.Gray. Eastern North America. Sterile fronds to 100 cm tall. Now accepted as a separate species, Osmunda spectabilis. There are three very similar species, Osmunda spectabilis, Osmunda lancea and Osmunda japonica. Recent genetic analysis (Metzgar et al., 2008) has shown that the New World varieties are in a clade that is sister to the Old World varieties of Osmunda regalis.