Etymology Aquilinum means eaglelike.

Description Rhizome: long-creeping, subterranean, commonly 10 cm deep, but up to 50 cm, jointed hairs.
Frond: 200 cm high by 90 cm wide, but with much variation in dimensions, deciduous, monomorphic, blade/stipe ratio: 1:1 to 2:1.
Stipe: base dark brown shading to pale green above, soft hairs, vascular bundles: numerous, U- or O-shaped in cross section.
Blade: 3-pinnate-pinnatifid, but variable, more and less divided, broadly triangular, large, slightly arching, papery to leathery, hairs on rachis, costae, and on lower surface of the blade, nectaries on the underside at the bases of the pinnae and costae.
Pinnae: 10 to 12 pair, lowest very large, strictly opposite or subopposite in some forms; costae rachis and costae grooved above; margins folding downwards; veins free, forked, except for a marginal strand.
Sori: continuous, along the margin, indusium: double, the outer false, reflexed, the inner distinct or absent, sporangia: brown, maturity: midsummer.

Culture Habitat: open, sandy, acid terrain. Distribution: cosmopolitan, except for alpine-arctic regions. Hardy to -35°C, USDA Zone 3.

Distinctive Characteristics Bracken is the most studied fern, and there are many more resources on the web than listed here. It is a popular subject because of its invasive, weedy nature.

Synonyms
Pteris aquilina Linnaeus