1 Plant minute, consisting of filaments or thalli (undifferentiated into leaves, stems, and roots), generally a single cell thick, usually with abundant single-celled gemmae (specialized budlike groups of cells for asexual reproduction), and superficially resembling bryophytes in lacking vascular tissue; [usually epipetric on vertical or overhanging bedrock; [Pteridophytes]

1 Plant more complex, with vascular tissue, with stems (or rhizomes), leaves, and roots, the leaves generally > 1 cell thick (except in sporophytes of Hymenophyllaceae), reproducing by spores; [growing in very diverse habitats, including on bedrock]; [Lycophytes, Pteridophytes].

  2 Plant of various habitats, including wetlands, where sometimes growing in soils saturated or intermittently flooded, but not aquatic.

    3 Leaves ‘un-fern-like’: unlobed, variously awl-shaped, scale-like, terete, strap-shaped, or palmately lobed; [Lycophytes or Pteridophytes]

    3 Leaves ‘fern-like’: variously lobed or divided, ranging from pinnatifid to 4-pinnate; [Pteridophytes].

      4 Leaf blades (not including the petiole) small, < 30 cm long or wide (some species will key either here or in the next lead).

        5 Epipetric or epiphytic, growing on rock, tree bark, walls, or over rock in thin soil mats or in small soil pockets

        5 Terrestrial, growing in soil, not associated with rock outcrops

      4 Leaf blades medium to large, > 30 cm long or wide.

          6 Epipetric or epiphytic, growing on rock, walls, over rock in thin soil mats or in small soil pockets, or on tree trunks

          6 Terrestrial, growing in soil, not associated with rock outcrops