Key to Wisconsin Osmunda

• 1a.Leaves once compound with deeply lobed pinnae; veins forking once from the midrib of each lobe; fertile fronds composed of 2-5 pairs of smaller fertile pinnae, greenish at first, turning dark brown, in the middle of the otherwise green frond O. claytoniana

• 1b.Leaves twice compound, except sometimes in young plants; many veins forking two to three times between the midrib and the margin; fertile pinnae, if present, usually borne at the apex of the frond and much smaller than the sterile pinnae O. regalis