Phegopteris

Patel, Nikisha R., Fawcett, Susan & Gilman, Arthur V., 2019, Phegopteris excelsior (Thelypteridaceae): A New Species of North American Tetraploid Beech Fern, Novon, A Journal for Botanical Nomenclature 27 (4), pp. 211-218 : 217

KEY TO NORTH AMERICAN PHEGOPTERIS

1. Blades of fronds elongate, widest toward the middle......................... P. decursive-pinnata (H. C. Hall) Fée

1 '. Blades of fronds widest at the base.

2. Blades of fronds usually slightly wider than long; all pinnae, including proximal pair, winged to rachis; proximal pinnae (2–)3X as long as wide............................................. P. hexagonoptera (Michx.) Fée

2 '. Blades of fronds longer than wide; pinnae winged to rachis except proximal pair not winged to rachis (rarely, more than one proximal pinna pair not winged in P. connectilis ); proximal pinnae 4–5X as long as wide.

3. Blade outline ovate, proximal pinnae strongly declined and adaxially inflexed, average 4X as long as wide; spore length averaging 55 ± 5.4 μ m...................................... P. connectilis (Michx.) Watt

3'. Blade outline triangular, proximal pinnae slightly to moderately declined and adaxially inflexed, average 5X as long as wide; spore length averaging 64 ± 4.6 μ m......... P. excelsior N. R. Patel & A. V. Gilman