An Illustrated Flora of the Northern United States, Canada and the British Possessions/Osmundaceae

Blades bipinnate, some of them fertile at the apex. Herbaceous blades bipinnatifid. Pinnae of sterile blade with a tuft of tomentum at the base; blades normally dimorphous. Pinnae of sterile blade lacking a tuft of tomentum at the base; blades normally fertile only in the middle.