| | 1. Sterile leaf part generally > 10 cm; leaf bud densely hairy; fertile leaf part aborted or well developed; leaf leathery, evergreen, each part generally ± 2–3-pinnate |
| B. multifidum |
| | 1' Sterile leaf part generally < 10 cm; leaf bud glabrous; fertile leaf part well developed; leaf herbaceous, deciduous, each part simple to ± 2-pinnate |
| |
| | 2. Sterile leaf part segments oblique-ovate to lanceolate-oblong, midribbed |
| B. pinnatum |
| | 2' Sterile leaf part segments generally spoon- to wedge-or fan-shaped, not midribbed |
| |
| | 3. Sterile and fertile leaf parts separated near to well below mid-leaf; blade tips coarsely lobed to irregularly angled or shallowly rounded |
| |
| | 4. Sterile, fertile leaf parts separated near to just below middle of leaf; full-sized blades oblong, non-ternate, segments irregularly angled, square or oblong; shady coniferous woods |
| B. montanum |
| | 4' Sterile, fertile leaf parts separated well below middle of leaf, generally at top of leaf sheath; full-sized blades oblong to ovate, ternate, segments wedge- to fan-shaped; open marshes, damp meadows |
| B. simplex |
| | 3' Sterile and fertile leaf parts separated near or generally above mid-leaf; blade tips finely, regularly, and deeply lobed |
| |
| | 5. Lower segments of sterile leaf part widely fan-shaped, margins at base meeting at 120–160° |
| |
| | 6. Plant slender, herbaceous-fleshy; sterile leaf part generally < 6 cm, < 2 cm wide, segments 3–5 pairs, ± well separated, outer margins generally finely crenate to dentate; fertile leaf part 1.3–3 × sterile leaf part; marshes, meadows |
| B. crenulatum |
| | 6' Plant robust, fleshy; sterile leaf part generally 6–10 cm, 2–4 cm wide, segments 4–9 pairs, generally touching to overlapped, outer margins generally entire; fertile leaf part 0.8–2 × sterile; dryish fields, meadows |
| B. lunaria |
| | 5' Lower segments of sterile leaf part narrowly fan- to wedge-shaped, margins at base meeting at 40–100(120)° |
| |
| | 7. Segments of sterile leaf parts distally angled, irregularly toothed, ascending, lower segments wedge-shaped, margins at base meeting at 40–90(120)°, basal often with scattered marginal sporangia |
| B. ascendens |
| | 7' Segments of sterile leaf parts distally rounded, ± smooth, not or ± ascending, lower segments ± fan-shaped, margins at base meeting at 50–100(120)°, basal without scattered marginal sporangia |
| B. minganense
|