Flora of the Southeastern United States
2022 Edition

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Key to Cystopteris

1 Indusia, rachises, and veins with stalked glands (these sometimes sparse in C. tennesseensis and C. laurentiana); bulblets often present on the rachis.
..2 Leaf blade 10-55 cm long, usually 2-3× as long as the reddish to tan petiole, lowest pair of pinnae the longest, thus the leaf widest at the base; bulblets usually present, smooth, green, 2-3 mm in diameter, usually on the rachis and the midrib; spores 20-38 μ long
..2 Leaf blade 6-25 cm long, usually about 1× as long as the dark brown petiole, thus the leaf widest above the base; bulblets present or absent, deformed and scaly, dark, < 1.5 mm in diameter, on the rachis only; spores 25-60 μ long.
....3 Leaves widest above the base; spores 49-60 μ long; [PA and IL northwards]
....3 Leaves widest at or near the base; spores 38-42 μ long; [PA, OH, IN, IL, WI and MN southwards]
1 Indusia, rachises, and veins eglandular; bulblets never present.
......4 Leaf blade (2.5-) 3-4× as long as wide; pinnae usually perpendicular to the rachis (or even reflexed); margins of pinnae serrulate, the teeth sharp; basal pinnules sessile, truncate to rounded at the base; indusium up to1 mm long, lanceolate; pinnae usually perpendicular to rachis; [on rock outcrops]
......4 Leaf blade 2-2.5 (-3)× as long as wide; pinnae usually at an acute angle to the rachis, curving toward the blade apex; margins of pinnae crenulate, the teeth rounded; basal pinnules short-stalked or sessile, rounded to cuneate at the base; indusium about 0.5 mm long, ovate to round; pinnae usually at an acute angle to the rachis; [on rock outcrops or forest floor].
........5 Rhizome long-creeping, the apex extending 10-60 mm beyond the last of the widely-spaced petioles (especially as seen from late spring to summer); rhizome covered with scales and tan to golden hairs; spores 20-32 μ long; leaves membranaceous in texture; basal pinnules conspicuously stalked; petiole green to tan, darkened at base; lowermost pinnules of each pinna deeply cut; [typically on forest floor, less commonly on rocks]
........5 Rhizome short-creeping, the apex extending only 1-5 mm beyond the last of the closely-spaced petioles; rhizome covered with scales, lacking hairs; spores 32-42 μ long; leaves thicker in texture; basal pinnules slightly stalked or merely cuneate to the base; petiole dark brown; lowermost pinnules of each pinna slightly lobed; [often on rocks, less commonly on forest floor]