Kingdom: Plantae
Division: Pteridophyta
Class: Polypodiopsida
Order: Polypodiales
Family: Blechnaceae
Genus: Blechnum
Species: B. colensoi
Binomial name: Blechnum colensoi
Synonyms: Blechnum patersonii, Lomaria patersonii var. elongata sensu, Lomaria heterophylla, Blechnum patersonii var. elongatum, Lomaria colensoi.
Common names: Colenso's hard fern, Colenso's Blechnum, Peretao, Petako.

Blechnum colensoi is a species of fern native to New Zealand with large dark green strap-like foliage. It is prostrate and slow creeping reaching a height of 0.4m with a spread of 1m. It's distributed throughout the North Island south from the Warawara Forest (Kaitaia), South Island, Stewart Islands, Chatham and Auckland Islands.
B. colensoi is usually found in dark areas usually within seepages, such as steep banks, waterfalls, river gorges and rocky overhangs. It also grows on the sodden ground within cloud forests.

For more information visit:  http://www.nzpcn.org.nz/flora_details.asp?ID=1543

Blechnum colensoi Peretao-001.JPG

The slender fertile pinnae with sterile fronds beneath.
Blechnum colensoi Peretao -002.JPG 

The top surface of a sterile frond
Blechnum colensoi Peretao-002.JPG

The underneath of a sterile frond.
Blechnum colensoi Peretao-003.JPG

Thanks to Wikipedia for text and information:

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