Blechnaceae
Netted veins along the axes of the blade to form a series of areoles (enclosed spaces) or a single continuous vein along which the sorus is borne, elongate sori with indusia opening toward midvein. Here 2 genera.

Blechnum Linnaeus

Deer fern

Etymology Greek: Blechnum is derived from the word blechnon, which is an ancient Greek word for ferns in general.
Description Rhizome: erect to creeping, scales brown or black.
Frond: evergreen, dimorphic, fertile leaves more erect and longer than sterile leaves.
vascular bundles: more than 2 vascular bundles arranged in arc.
Blade: pinnatifid to 1-pinnate, ovate, leathery, young fronds are often red.
veins sterile:free, often forked; fertile: veins of fertile leaves united to form sorus-bearing secondary vein parallel to costa or costule.
Sori: elongate, continuous, on both sides of the costae, indusium: flap-like, opening towards the costa.
Distinctive Characteristics Emerging fronds in the genus are usually red or reddish, loosing the color when fully expanded.
Blechnum
Blechnum spicant. a) free venation in sterile pinna; b) netted venation of fertile pinna.  Illustration from Scandinavian Ferns by Benjamin Ĝllgaard and Kirsten Tind, Rhodos, 1993.

Woodwardia Smith

Chain fern

Etymology Named for Thomas Jenkinson Woodward, (1745-1820), an English botanist.
Description Rhizome: long-creeping, scales.
Frond: deciduous, monomorphic or dimorphic.
Stipe: scaly or not, vascular bundles: variable.
Blade: pinnatifid to 1-pinnate-pinnatifid, thin-textured, scales on emergence in W. areolata, but glabrous later.
veins free or partly netted.
Sori: in chainlike rows, but distinct, along the costae, indusium: flap-like, opening towards the costa.
Distinctive Characteristics Linear sori adjacent to the costae characterize Woodwardia.
W. virginica: chains of sori
Woodwardia is characterized by chains of sori as shown here.  Photo: Dennis Woodland

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