[Athyrium angustum (Willd.) C. Presl, moreAthyrium angustum f. confertum Butters, Athyrium angustum f. elegans Butters, Athyrium angustum f. laciniatum Butters, Athyrium angustum var. angustum (Willd.) C. Presl, Athyrium angustum var. laurentianum Butters, Athyrium angustum var. rubellum (Gilbert) Butters, Athyrium angustum var. subtripinnatum Butters, Athyrium filix-femina var. angustum (Willd.) G. Lawson, Athyrium filix-femina var. michauxii (Spreng.) Farw., Athyrium filix-femina var. rubellum Gilbert]
Petiole (7--)15--55 cm; scales brown to dark brown, linear-lanceolate, 8(--10) × 2 mm. Blade elliptic, 2-pinnatifid to 2-pinnate, (20--)30--75 × (5--)10--35 cm, moderately narrowed proximally, broadest near or just below middle, apex acuminate. Pinnae short-stalked or sessile, oblong-lanceolate. Pinnules decurrent onto costal wing or sessile, linear to oblong, base unequally cuneate, apex obtuse to acute or in larger leaves acuminate, lobed halfway or more to costules. Rachis , costae, and costules glabrous or with pale glands. Sori straight, less frequently hooked at distal end or horseshoe-shaped; sporangial stalks bearing glandular hairs; indusia irregularly dentate, ± ciliate. Spores yellow or brown. 2 n = 80. Moist woods, swamps, thickets; 0--1100 m; Greenland; Man., N.B., Nfld., N.S., Ont., P.E.I., Que., Sask.; Conn., Del., Ill., Ind., Iowa, Maine, Md., Mass., Mich., Minn., Mo., Nebr., N.H., N.J., N.Y., N.C., N.Dak., Ohio, Pa., R.I., S.Dak., Vt., Va., W.Va., Wis.
Perennial fern 27 cm - 1.3 m tall Leaves: several, clustered, erect, herbaceous, deciduous, green, 20 - 75 cm long, 10 - 35 cm wide, widest near or just below middle, elliptic in outline with long pointed tip, but twice pinnately compound, hairless or sometimes with a few pale glands on the "midrib" (rachis). Rhizome: short-creeping, ascending at tip, and covered with scales. Leaf stalks: clustered near rhizome tip, erect, swollen at base, dark red-brown or black at bottom then straw-colored, 7 - 55 cm long, with two rows of teeth, and small (0.8 - 1 cm long, 2 mm wide), linear to lance-shaped, brown to dark brown scales at stalk base. Spores: 64 per sac, yellow, all of one kind, single-sectioned (monolete), oblong or kidney-shaped, and wrinkled. The spores give rise to the gametophyte (the sexual phase of the plant), which is small, green, heart-shaped, hairless or often with glands or hairs, and sits above the ground.
Similar species: Athyrium filix-femina var. angustum is probably most similar to Deparia acrostichoides, but that species has a more horizontal and creeping rhizome, pinnae that are not fully divided into pinnules but only deeply lobed into shallow-toothed segments, much shallower grooves on the underside of the pinnae midveins (costae) that do not continue into the groove on the main leaf "midrib" (rachis), and the rachis, costae, and main veins are covered with copious multicellular hairs. One may also confuse this species with some sterile leaves of Matteuccia struthiopteris var. pensylvanica, but that fern will never have spores and sori borne on the expanded green leaves, but rather on separate narrower, darkened, hardened leaves. Further, some may confuse this fern with two of our spiny-toothed Dryopteris species, D. intermedia and D. carthusiana, but both of those ferns have their spores arranged in rounded clusters (sori), which are covered by somewhat kidney-shaped flaps of tissue (indusia), which have a distinct notch that attaches to the leaf blade tissue.
Habitat and ecology: Occasional, but becoming more rare since it requires undisturbed mesic woods.
Occurence in the Chicago region: native
Notes: This fern has been categorized under many different varieties of the species A. filix-femina, but the correct name is as given above. Another variety, A. filix-femina var. asplenioides, occurs to the south to of the Chicago Region. It differs from our variety by having light brown to brown leaf stalk scales, the leaves are broadest just above the base, the pinnae are usually stalked, the pinnules are wider and more triangular, and the spores are dark brown.
Author: The Field Museum
From Flora of Indiana (1940) by Charles C. Deam
Infrequent in moist, rich woods throughout the state. [Deam also recognized additional varieties: elatius and rubellum.] Variety elatius is infrequent throughout the state and found in rich beech and sugar maple and white and black oak woods. Variety rubellum is infrequent throughout the state. The habitats of my specimens are notable because of lack of uniformity. I have one specimen from a tamarack bog and others from low, flat woods in hard, white clay soil, dry black and white oak woods, bluffs of the Ohio River, and rich, moist woods.
Petiole commonly ca half as long as the blade, the basal scales often blackish; blade widest near the middle, the fourth or fifth pair of pinnae the largest; cilia of the indusia eglandular; spores yellowish to brownish. Nf. and Que. to Ont. and S.D., s. to Md., Va., Ky., and Mo. (A. angustum)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.