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16 FERNS AND FERN ALLIES 1a. Stems jointed, hollow, green (except the fertile stems of Equisetum arvense, which are yellowish brown), the nodes circled by sheaths. Equisetaceae, HORSETAIL FAMILY 1b. Stems not jointed, seldom green; sheaths absent. . . . . . . . . . . . . . . . . . . . . . . . . . . (2) 2a. Plants aquatic, inhabiting lake shores or submerged in ponds and lakes . . . . . . . . (3) 2b. Plants terrestrial, growing on soil or rocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (4) 3a. Leaves grass-like, their bases swollen, each bearing a pair of sporangia, the whole forming an onion-like bulb; plants submerged in shallow water of mountain lakes and ponds for the greater part of the growing season. Isoëtaceae, QUILLWORT FAMILY 3b. Leaves with distinct petioles and blades, the blades 4-parted, resembling a 4-leaf clover ; spores borne at the base of the plant in round nut-like “sporocarps;” borders of ponds and sandy streamsides at lower altitudes. Marsileaceae, PEPPERWORT FAMILY 4a. Leaves very numerous, lanceolate or linear, often bract-like, sessile, spirally or oppositely arranged in 4 to many ranks upon branched perennial stems. . . . . . . . . . . . (5) 4b. Leaves relatively few, broad or ± dissected (except in Asplenium septentrionale, the GRASS FERN, which has linear leaves), arising from an underground stem . . . . . . . (6) 5a. Leaves minute (less than 3 mm long). Selaginellaceae, LITTLE CLUB-MOSS FAMILY 5b. Leaves larger (5 mm–1 cm or more long). Lycopodiaceae, CLUB-MOSS FAMILY 6a. Fronds (the “leaves” of ferns) narrowly linear, divided towards the tip into a few narrow forks. Asplenium septentrionale, in Aspleniaceae, SPLEENWORT FAMILY 6b. Fronds broader, ± dissected (fern-like) [entire in Ophioglossum] . . . . . . . . . . . . . . . (7) 7a. An entire branch of each frond completely altered in appearance, modified for spore production, the remainder of the frond green and not producing spores. Ophioglossaceae, MOONWORT FAMILY 7b. Fronds without conspicuously altered branches; entire fronds modified for spore production (there being 2 forms of fronds) or spores borne on the undersides of relatively unmodified fronds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (8) 8a. Fronds of 2 kinds, the sterile ones short, yellow-green, with much-divided pinnae, their ultimate divisions blunt-tipped; fertile fronds taller, with pod-shaped pinnules. Cryptogrammaceae, ROCK BRAKE FAMILY 8b. Fronds all similar, whether fertile or sterile. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (9) 9a. Fronds with the lower pair of branches ± equaling the central branch or facing forward , creating the illusion of a 3-branched frond. . . . . . . . . . . . . . . . . . . . . . . . . . (10) 9b. Fronds distinctly pinnate, with 1 main axis from which the pinnae arise along the sides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (11) 10a. Fronds tall and coarse, forming thicket-like stands; sporangia, when present, borne on the infolded edges of the pinnules. Hypolepidaceae, BRACKEN FAMILY 10b. Fronds small, delicate; sporangia, when present, borne on the flat undersides of the pinnules. Gymnocarpium, in Athyriaceae, LADY FERN FAMILY 11a. Fronds with submarginal sori, the indusium formed by the rolled or folded edge of the pinnule. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (12) 11b. Fronds with the sori on the face of the pinnule . . . . . . . . . . . . . . . . . . . . . . . . . . . (13) 12a. Pinnules large, thin, smooth, green, fan-shaped or reniform. Adiantaceae, MAIDENHAIR FAMILY 12b. Pinnules small, often thickish, hairy or scaly or waxy-coated below. Cheilanthaceae, LIP FERN FAMILY 17 Ferns and Fern Allies 13a. Frond merely deeply pinnatifid, the bases of the pinnae fused to the stipe . . . . . (14) 13b. Frond distinctly pinnate, the pinnae not fused to the sides of the stipe . . . . . . . . (15) 14a. Frond lanceolate or oblong, evergreen, the pinnae not divided into pinnules. Polypodiaceae, POLYPODY FAMILY 14b. Frond triangular, not evergreen, the pinnae divided into pinnatifid pinnules. Thelypteridaceae 15a. Sori linear-elliptic; indusium curved, crescentic, or absent. Athyriaceae, LADY FERN FAMILY 15b. Sori round or greatly elongate; indusia not crescent-shaped. . . . . . . . . . . . . . . . . (16) 16a. Plants large, stout; indusium forming a somewhat circular shield, attached at the sinus. Dryopteridaceae, SHIELD FERN FAMILY 16b. Plants small, delicate; indusia not as above. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (17) 17a. Sori greatly elongate, with a flap-like indusium attached along a vein. Aspleniaceae, SPLEENWORT FAMILY 17b. Sori round, with or without indusia or, if slightly elongate, without indusia . . . (18) 18a. Indusium cup-like, attached at the center below the sporangia, deeply cleft at maturity ; pinnae thickish, widest above the middle. Woodsiaceae, WOODSIA FAMILY 18b. Indusium hood-like, attached by one side at the base, not cleft at maturity; pinnae thin, broadest below the middle or at the base. Cystopteris in Athyriaceae, LADY FERN FAMILY ADIANTACEAE Newman 1840. MAIDENHAIR FAMILY (ADI) Maidenhairs are the most delicate and rarest of our ferns. The fronds are sometimes branched once dichotomously, with the pinnae radiating from one side of each branch like the comb of a Spanish mantilla. In our species the frond has 1 main branch, from which the pinnae arise on each side in a...

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