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Click the number at the start of a key lead to highlight both that lead and its corresponding lead. Click again to show only the two highlighted leads. Click a third time to return to the full key with the selected leads still highlighted.

Key to Myriopteris

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1 Lower leaf surfaces with a few obscure hairs or glabrescent.
  2 Basal pinnae inequilateral (the basalmost basiscopic pinnules much larger than the basalmost acroscopic pinnules); leaf blade outline ovate to deltate, 1.5-2.5× as long as wide, 5-15 cm wide
  2 Basal pinnae equilateral, the basiscopic and acroscopic pinnules approximately equal; leaf blade outline lanceolate, 3-6× as long as wide, 1-7 cm wide.
    3 Rhizomes short-creeping, usually 4-7 mm in diameter; pinna axes (costae) green on the upper surface for most of their length; spores 32 per sporangium
    3 Rhizomes long-creeping, usually 1-3 mm in diameter; pinna axes (costae) black on the upper surface for most of their length; spores 64 per sporangium
1 Lower leaf surfaces obviously pubescent (tomentose, villous, or lanose).
      4 Petiole and rachis with hairs only (as seen at 10× magnification), the hairs segmented by prominent cell walls; margins of leaf segments more-or-less under-rolled but not modified into a scarious flap, the sori often exposed at maturity.
        5 Leaves 3-pinnate at base; ultimate segments 1-3 mm long, round (beadlike); spores 32 per sporangium
        5 Leaves 2-pinnate-pinnatifid (rarely 3-pinnate); ultimate segments 3-5 mm long, elongate (not bead-like); spores 64 per sporangium
      4 Petiole and rachis with a mixture of flattened scales (in M. tomentosa these very narrow and superficially mistakable for hairs) and hairs (as seen at 10× magnification); margins of leaf segments modified into a scarious flap (false indusium) partially to fully covering the sori.
          6 Ultimate leaf segments scabrous (with stiff hairs) on the upper surface
          6 Ultimate leaf segments smooth, lacking stiff hairs.
             7 Rachis scales ca. 0.1 (-0.3) mm wide, linear; leaf blade villous-tomentose above, appearing whitish or gray-green
             7 Rachis scales (0.2-) 0.4-1.0 mm wide, lanceolate; leaf blade nearly glabrous above, appearing green
               8 Rhizome slender and widely creeping, leaves scattered; rachis scales ovate to lanceolate, long ciliate
               8 Rhizome short and stout, leaves strongly clustered; rachis scales linear to lanceolate, lacking cilia (except maybe a few near the base)
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