Adiantum Linnaeus (Pteridaceae) Earlier placement: Adiantaceae, Sinopteridaceae, Parkeriaceae, Lindsaeaceae

Maidenhair fern

Etymology Adiantum is from the Greek, adiantos, meaning unwettable, referring to the water-repellent fronds.
Description Rhizome: suberect to long-creeping, absent or hairy or scaly.
Frond: deciduous, monomorphic.
Stipe: chestnut brown to dark purple, grooved above, glabrous or few scales, vascular bundles: 1 or 2.
Blade: 1-3 pinnate or pedate, lanceolate, ovate, trowel-shaped, or fan-shaped, membranaceous to papery, commonly glabrous.
segments round, fan-shaped, rhombic, or oblong with marginal teeth, lacking a midrib, veins free, forking.
Sori: sporangia, submarginal, indusium: false, inrolled margins, sporangia: yellow or yellowish brown.
Distinctive Characteristics FNA states that sporangia borne on the lower surface of the false indusium are both necessary and sufficient to define the genus. However, lacking a high-powered lens, the amateur will need additional criteria. The lack of a midrib in the ultimate segments is unique among the hardy ferns here.
Adiantum pedatum
Adiantum pedatum. False indusium.  Photo by Rod Tulloss, Environmental Commission of the Borough of Roosevelt and the Fund for Roosevelt, Inc.
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