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 Sterile leaf blade (trophophore) leaflets linear to narrow-ovate, the apex obtuse to acuminate, the margins shallowly to deeply lobed; at least the tip of the sterile leaf blade (trophophore) reflexed in bud.
..2 Sterile leaf blade (trophophore) deltate (widest at base), with 3 axes, usually ± sessile; fertile leaf (sporophore) reflexed in bud
..2 Sterile leaf blade (trophophore) oblong to ovate, with 1 main axis, usually stalked; fertile leaf (sporophore) mainly erect in bud, only the very tip curved over
1 Sterile leaf blade (trophophore) leaflets nearly orbicular to obovate or flabellate, the apex rounded to truncate, the margins entire or distally few-lobed; sterile leaf blade (trophophore) and fertile leaf (sporophore) erect in bud or only the extreme tip of the sterile leaf blade (trophophore) slightly inclined.
....3 Sterile leaf blade (trophophore) usually with evident lobes, the first and second pairs of leaflets separated by a similar or slightly longer distance than the second and third pairs of leaflets.
......4 Lowest pair of sterile leaf blade (trophophore) leaflets slightly, if at all, larger and more cleft or lobed than next apical pair; sterile leaf blades (trophophores) typically with small, narrow-flabellate terminal segments
......4 Lowest pair of sterile leaf blade (trophophore) leaflets (or lobes in dwarf individuals) obviously larger and more complex in most plants then next apical pair; many sterile leaf blades (trophophores) with a characteristically broad, rounded to obtuse, terminal segment
....3 Sterile leaf blade (trophophore) very slender and simple to obscurely lobed or with evident lobes, in the latter case usually with a greater distance between the first and second pairs of leaflets than between the second and third pairs of leaflets counting from the base.
........5 Lowest pair of sterile leaf blade (trophophore) lobes or leaflets, when present, often noticeably larger and more complex than the next apical pair; lobes varying from oblong to flabellate to reniform; stalk of sterile leaf blade (trophophore) usually borne near base of plant (sometimes toward mid-height); [primarily of open areas such as fields, shores, and banks]
........5 Lowest pair of sterile leaf blade (trophophore) lobes or leaflets, when present, not obviously larger than the next apical pair; lobes on well-developed plants usually square-oblong to obovate-oblong; stalk of sterile leaf blade (trophophore) inserted high on common stalk, usually at or above mid-height of plant; [primarily of forested wetlands]