Species of the Month - November 2016
As the year draws to
a close, many flowering plants die down or lose their defining
features, but most ferns keep in good shape throughout the winter,
including the Hartstongue Fern which is fully evergreen. It is
very easily recognised as it is the only fern with completely undivided
underside of the fronds bear linear sori containing the spores.
When young these are covered with a silvery indusium, which opens when
the spores are ready for release. There are actually two sori
each vein, but they are so close together that as soon as the
sporangia begin to expand, the pair of sori appear as a single brown
Fully-expanded fronds in early August, still with a fresh green colour due to being in a sunny location. The fern normally prefers shaded situations where it develops a leathery appearance. It needs neutral to alkaline conditions and is absent from acidic rocks unless they are flushed with base-rich seepage, as often happens in the gorges of hill burns. It is common on mortared walls but is unlikely to be found on dry stone walls unless they are of limestone.
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Nov 13: Large stand in mixed broadleaved wood on east side of Seil Sound, James Fenton
Nov 29: Seen on several mortarted walls in Oban, Carl
Nov 30: Seen in Onich, Sallie