× Osmunimunda ruggii (R.M.Tryon) X.Wan & Li Bing Zhang, comb. nov.

Basionym: Osmunda × ruggii R.M. Tryon (1940: 65) ≡ “ × Osmuntonia ruggii (R.M.Tryon) Hong M.Liu, Schuettp. & H.Schneid. ” (2020: 999), nom. inval.

Type:— USA. Connecticut: Hartford, cult., 20 June 1934, H. G . Rugg, s.n. (holotype GH00021739) .

Notes: This nothospecies is a hybrid between Claytosmunda claytoniana (Linnaeus 1753: 1066) Metzgar & Rouhan in PPG I (2016: 594) and Osmunda regalis var. spectabilis (Willdenow 1810: 98) A. Gray (1856: 600) . It has intermediate morphology of the parents, such as fertile fronds, segment size, vein branching, and segment margins. Although its parents occur together in a large area, mature hybrids are difficult to find due to its rarity. Perhaps they are incompatible with other plants, or there are strong incompatibility barriers between the parents (Tryon 1940, Wagner et al. 1978).

Distribution: Northeastern U.S.A.