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NZ Plants

Blechnum colensoi - peretao, Colenso's hard fern

Hard fern family: Blechnaceae

  • Left: three stages of sterile frond development. Right: fertile frond

    I MacDonald

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  • Mature sterile frond with leaflets

    L Jensen

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  • Frond stalk (stipe) with scales

    L Jensen

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  • Frond midrib (rachis), upper surface

    L Jensen

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  • Frond rachis, upper surface

    L Jensen

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  • Frond rachis, lower surface

    L Jensen

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  • Rachus upper surface, hairs

    L Jensen

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  • Leaflet margin, upper surface

    L Jensen

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  • Leaflet margin with water secreting glands (hydathodes)

    L Jensen

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  • Leaflet margin, lower surface

    L Jensen

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  • Fertile frond

    I MacDonald

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  • Fertile frond, upper surface of rachis

    L Jensen

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  • Fertile frond, lower surface of rachis and leaflet

    L Jensen

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  • Fertile leaflet with indusium covering sporangia underneath

    L Jensen

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Blechnum colensoi has a stout, erect stem with dissimilar sterile and fertile fronds (dimorphic).
The elliptic sterile fronds are dark-blue green and leathery, undivided or divided once into a small number of broad leaflets. Fertile fronds are extremely slender with long terminal leaflets.
An endemic fern found in wet lowland to mountain forest from Auckland southwards.
 

Vegetative characteristics

Fertile frond and sporangia

Plant form: a short, erect trunk with fronds up to 500 mm long

Frond appearance: about as long as sterile, very narrow, with long, narrow leaflets

Frond stalk, midrib: scales

Sporangium location: on lower frond surface

Sterile frond shape: elliptic to rhomboid

Sporangium position: leaflet margin

Frond blade: undivided or pinnate (divided 1 x into leaflets or pinnae)

Sporangium distribution: in groups (sori)

Frond surface: leathery

Sorus shape: in a continuous line either side of midrib

Leaflets: oblong, smooth margins and a tapering, pointed tip; attached along leaflet base (adnate)

Sorus covering: linear, opening toward midrib

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