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Topic: button fern

Is part of topic Common New Zealand ferns

tarawera
Pellaea rotundifolia

Recognition: small ground fern, with linear fronds that are once-divided into dark green, round to oblong segments.  The sporangia (which produce spores) are aggregated into sori that line the margins of the undersides of the frond segments.

Distribution/ecology: only found in New Zealand. In forest throughout.  Most common in drier, fertile habitats.

Relationships: only one other Pellaea definitely occurs in mainland New Zealand: Pellaea calidirupium, which differs in having appressed (rather than spreading) scales on the stems, sori that extend right around the apices of the frond segments (rather than having a gap at the apex), and in often having an enlarged terminal frond segment.  Pellaea calidirupium is generally in even drier, more open habitats.

Pellaea falcata is sometimes also recognised from mainland New Zealand, but the limits between this principally Australian species, Pellaea rotundifolia, and the Australian Pellaea nana are unclear.

The boundary between Pellaea and Cheilanthes and a suite of other genera is also unclear, but they do belong to the Pteridaceae fern family, whose other indigenous New Zealand representatives are Adiantum, Anogramma, and Pteris.

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