English name: Brittle Bladder-fern
Gaelic name: Frith-raineach

Atlas of Ferns:
Pre 1950 record: NG41.
Post 1950 records: NG14, 15, 23, 24, 26, 32-36, 42, 44-47, 51-55, 60-62, 72. 

British Pteridophyte Records:
BPS Bulletin Volume 2, Number 1, (1979): NG43 C. W. Murray.
The Fern Gazette Volume 12, Part 5, (1983): NG71 C. W. Murray.

Botanist in Skye: Recorded in all hectads except NG25, 37, 50, 56, 63, 65.

New Atlas:
1950-1969: NG14, 15, 23, 26, 33, 34, 35, 36.      
1970-1986: NG24, 43, 44.   
1987-1999: Recorded in all other hectads except NG25, 37 and 50.

Altitude distribution on Skye
Minimum: 22m.
Maximum: 490m.

Cystopteris fragilis occurs on limestone pavements with A. ruta-muraria, A. viride, A. scolopendrium, A. trichomanes and Polystichum aculeatum. At higher altitudes (above 300m) on Jurassic limestone outcrops in Coire Uaigneach, Blà Bheinn, and on the calcareous cliffs of Sgùrr Mor, The Storr and the Quirang it occurs with A. viride, A. trichomanes and Polystichum lonchitis. In Rodwell (ed.) (1992, 2000) it occurs in the U17b and OV40 communities. In Birks (1973) it occurs in the Asplenium trichomanes-Fissidens dubius, Saxifragetum aizoidis and Sedum rosea-Alchemilla glabra Associations and as a part of the Limestone Pavement Community.

In their report on the BPS Centenary field meeting in the 1991 BPS Bulletin Clive Jermy and Anthony Pigott recorded finding a Cystopteris with very finely dissected fronds very similar to C. alpina a plant of the Alps of Europe but not recorded for Britain.

NOTE: C. fragilis is a very variable species, in Britain it occurs as either a tetraploid, 2n=168, a hexaploid, 2n=252, or a pentaploid hybrid with 2n=210 chromosomes. In The Ferns of Britain and Ireland (1997) C. Page states that plants have been found whose frond type looks like C. fragilis but whose spores are like those of C. dickieana. This is presumably the reason for the statement in his book on Ferns in the New Naturalist Library (1988) that in at least one alpine site on Skye plants which may be Cystopteris dickieana occur.