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Claytosmunda (Y. Yatabe, N. Murakami, & K. Iwatsuki) Metzgar & Rouhan Rouhan. Interrupted Fern.

A monotypic genus, a perennial fern, of e. North America and e. Asia. The species Claytosmunda claytoniana has traditionally been treated within a broadly conceived Osmunda, but has recently been separated based on the age of the clade separation and the profound morphological differences between it and other clades in the family (see discussion under Osmundaceae).

ID notes:Claytosmunda is the most "upland" and least robust of our species of Osmundaceae. Fertile leaves of Claytosmunda are unique in the placement of brown (later shriveled) spore-bearing pinnae in the middle of the blade, with sterile, green pinnae above and below the fertile pinnae. Sterile plants (which are frequent, and entire populations sometimes lack fertile plants) can closely resemble sterile plants of Osmundastrum cinnamomeum, but can be told by the lack of a tuft of hairs on the lower side of the junction of each pinna to the rachis. Additionally, Claytosmunda claytoniana has a smoother gestalt and overall rounder pinna and pinna lobe tips, while Osmundastrum cinnamomeum has a hairier gestalt and overall more pointed pinna tips and pinna lobe tips.

Ref: Kramer & Green (1990); Lellinger (1985); Metzgar et al. (2008); PPG I (2016); Schneider et al. (2015); Tsutsumi et al. (2011); Whetstone & Atkinson (1993) In Flora of North America Editorial Committee (1993b); Yatabe, Nishida, and Murakami (1999); Zhang, Iwatsuki, & Kadokawa in FoC (2013). Show full citations.

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