Leaves pinnate-pinnatifid; petioles ca. 1/3 length of blades, winged, with light brown hairs, becoming glabrate. Sterile leaves elliptic to oblong, ca. 0.5--1 m; pinnae broadly oblong, lacking persistent tuft of hairs at base; ultimate segments with base truncate, margins entire, apex rounded. Fertile leaves with greatly reduced, sporangia-bearing medial pinnae that wither early, giving appearance of no middle pinnae (hence the vernacular name, interrupted fern). Sporangia greenish, turning dark brown. 2 n =44. Sporulation early spring--midsummer; 0--2300 m; St. Pierre and Miquelon; Man., N.B., Nfld., N.S., Ont., P.E.I., Que.; Conn., Ill., Ind., Iowa, Ky., Maine, Md., Mass., Mich., Minn., Mo., N.H., N.J., N.Y., N.C., Ohio, Pa., R.I., Tenn., Vt., Va., W.Va., Wis.; Asia Osmunda claytoniana is sparingly cultivated as an ornamental.

Much like no. 2 [Osmunda cinnamomea L.]; lvs soft, dull blue-green, foreshortened and blunt at the tip, as also the individual pinnae; rachis soon glabrate; segments of the sterile pinnae slightly hairy but not ciliate; outer lvs usually sterile, the inner larger and with 1-5 pairs of fertile pinnae near the middle of the blade; fertile pinnae to 6 נ2 cm, much smaller than the vegetative ones above and below; sporangia dark brown; 2n=44. Open, moist woods and margins of swamps, in subacid or neutral soil; Nf. to Ont. and Minn., s. to Ga., Tenn., and Ark.; e. Asia. Ours is var. claytoniana. A hybrid with no. 1 is O. زuggii R. M. Tryon.

Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.

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