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DescriptionThis perennial fern consists of a single sterile leaf and a single fertile leaf that bears the spores; the latter is not always produced. When both types of leaves are present, they are joined together at the bases of their petioles; this typically occurs close to the ground. The blade of the sterile leaf is bipinnate-pinnatifid or tripinnate-pinnatifid in its structure; it spans up to 6" long and 6" across. This blade is divided into 1-3 major divisions; each division has a deltate shape in outline, a bipinnate-pinnatifid structure, and a short stalk at its base. Each major division of the sterile leaf has up to 7 pairs of leaflets; the lower leaflets are stalked, while the upper leaflets are sessile. The lower leaflets and some of the upper leaflets are divided into up to 7 pairs of subleaflets that are oval to oblong-lanceolate in shape; usually the terminal subleaflets are larger and more elongated than the lateral subleaflets. The subleaflets and undivided upper leaflets have finely serrated or crenate margins; sometimes they are irregularly cleft into smaller lobes. The sterile leaf blade is evergreen; it is medium green during the autumn, but becomes bronze-colored during the winter (hence the common name). The petiole of the sterile blade is 2-6" long, light green or light bronze, and slightly succulent; both the sterile blade and its petiole are glabrous. The fertile leaf blade has a very different appearance from the sterile blade; this blade has a bipinnate or tripinnate structure, but it is contracted into sporangia-bearing branches. The fertile leaf blade is up to 8" long and 4" across (excluding its petiole); this leaf blade is initially medium green, but it later becomes tan or brown. The lateral branches and tip of the fertile blade bear dense rows of small globoid sporangia that are yellow; both the fertile leaf blade and sporangia are glabrous. During the late autumn or winter, the sporangia split open to release their minute spores to the wind. The petiole of the fertile leaf is 6-12" long; it is light to medium green, glabrous, and slightly succulent. The root system consists of fibrous roots that are fleshy and shallow.