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.
1 Vegetative leaves monomorphic, spirally arranged around the stems; leaves acuminate and with a white or translucent apical hair-tip (the hair-tip rarely lost); fertile branch tip only slightly differentiated from the sterile portions of the stems; rhizophores dorsal (initiated from the upper side of the stems), borne either along the stems or only from rhizome-like stems; rhizophores medium-fine, 0.2-0.45 mm in diameter
1 Vegetative leaves dimorphic, in 4 ranks, the ventral pair spreading laterally, the dorsal pair ascending, the pairs different in shape and/or size (anisophyllous); leaves acute, mucronate, lacking a white or translucent apical hair-tip; fertile branch tips strongly differentiated (into strobili) from the sterile portions of the stem; rhizophores either dorsal or ventral, borne along the stems; rhizophores either very fine or medium fine, 0.02-0.4 mm in diameter, or coarse, 1-3 mm in diameter.
..2 Rhizophores dorsal (initiated from the upper side of the stems); stems articulated with a swelling near branching nodes; rhizophores 1-3 mm in diameter
....3 Sporophylls dimorphic; megaspore surfaces tuberculate, papillate, or very finely reticulate; [non-native species used horticulturally and sparingly spreading or naturalizing]
....3 Sporophylls monomorphic; megaspore surfaces reticulate; [native species; collectively widespread and common]