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NZ Plants

Adiantum formosum - giant maidenhair fern

Familay name: Pteridaceae

Adiantum formosum is a terrestrial fern with long-creeping stems (rhizomes). The frond stalk (stipe) has a rough surface but is hairless while the upper frond axis (rachis) is hairy with dark green oblong leaflets that are often hairy on the under surface.
Uncommon, found on the North Island as localised populations in shaded forest.

Vegetative characteristics

Fertile frond and sporangia

Plant form: creeping stems with fronds up to 100 cm tall

Frond appearance: similar to sterile frond

Frond stalk, midrib:stipe, rough; rachis and leaflet midribs with hairs

Sporangium location: on lower frond surface

Frond shape: broadly oval

Sporangium position: in shallow notch beneath reflexed leaflet margin

Frond blade: 3-4-pinnate (divided 2-4x into leaflets or pinnae) at base

Sporangia distribution: in groups (sori)

Frond surface: hairs on lower surface in some

Sorus shape: circular

Leaflets: oblong, irregularly lobed outer margin;  stalk attached at one end

Sorus covering:  crescent-shaped marginal flap