Nature Notes from Skye
(and occasionally other places)

Sat 18 Sep 2004

This Scottish branch of the British Pteridological Society held a field meeting on Skye this weekend.  The weather was not very kind, but a good time was had by all.  We started out at Ord in Sleat, where we admired the Tunbridge Filmy Fern, Wilson's Filmy Fern, Hay-scented Buckler Fern and Green Spleenwort, among others.  (I showed some of the Ord ferns on 10 July)  We were also treated to the latest thinking on the difficult Dryopteris affinis group by a leading expert in the field, and shown "classic" specimens of D affinis ssp borreri (below left) and ssp affinis (below right), which are the two common kinds in Skye, so I took the opportunity to get definitive photos of these two subspecies.

Dryopteris affinis ssp borreri   Dryopteris affinis ssp affinis

Borreri is the one found more often in woods and shady places, and often has an arching habit, with the basal pinnae deflexed and broader than the next pair of pinnae up.  The pinnule tips are squared off and have acute tips to their teeth.  The indusia roll up so that the sporangia are visible as a ring around them.

Affinis is the one found in tall upright clumps out in the open, and most of the conspicuous yellowish tufts you see on the hillsides in early summer are this subspecies.  The pinnule ends are rounded.  The indusia split radially and persist on the dead leaves.  The basal pinnule of the lowest pinna is joined to the midrib along its edge, whereas in Borreri it is usually detached.

However there are many intermediates and specimens that cannot be determined.  You have to take into account a range of characters and base your identification on the majority of them.

Trichomanes speciosum gametophyte   Trichomanes speciosum gametophyte

Next we went to look for the gametophytes of the Killarney Fern.  This was the highlight of the outing for me, as I knew that even if I found these things on my own one day I'd never be able to recognise them.  They were at the far end of a long narrow cave, in extreme darkness, although after we'd all queued up to visit the ones at the back of the cave we did find some more nearer the front.  Obviously very difficult to photograph, and I've included 4 photos here as they may be of interest to any of the group who see this page.  The plant forms mats of tangled filaments looking like a small moss or alga.  The one on the left above is a mat at the back of the cave and the one on the right is nearer the front.

Trichomanes speciosum gametophyte   Trichomanes speciosum gametophyte

These are slightly more close-up pictures, both were at the back of the cave, with someone shining a torch on the plant which accounts for the yellowish areas in both pictures.  The first is taken with flash and the second without.  I hope to go back there some time soon with a really powerful torch and take good close-ups showing the structure of the plant more clearly.

A little backgound detail.  Ferns have two generations, the sporophyte, which is the plant we see and recognise as a fern, and the gametophyte, which is very small and never normally noticed (I have never knowingly seen any fern gametophyte in the wild until today).  The Killarney Fern is one of the British Isles' rarest ferns and was made even rarer by the activities of collectors, so that today its few remaining locations (which do not include Skye) are a closely-guarded secret.  This applies to the sporophyte of course.  Until recently it was assumed that the gametophyte had the same distribution as the sporophyte, as with any other fern.  But in the early 1990s botanists began to find the gametophyte in places where the sporophyte had never been known, and as awareness of this possibility increased, more and more examples were found from a variety of places across the British Isles, making it clear that the gametophyte was far more widespread than the sporophyte could ever have been within historical time.

Uniquely among British ferns, the Killarney Fern gametophyte has the ability to reproduce vegetatively without going through a sporophyte generation.  Furthermore, these newly discovered free-living gametophytes seem incapable of producing a sporophyte even when given every stimulus to do so in cultivation.  In appearance they are the sort of thing that few botanists would bother with, just one of many kinds of green fuzz on the walls of a cave, but in status they are of huge interest to anyone interested in ferns or vascular plants generally, and it was a great thrill to see them.

Pellia endiviifolia   Preissia quadrata possibly

This beautiful liverwort (above left) was growing in the same cave.  It is Pellia endiviifolia, and the small branchlets seen in the picture only grow in autumn, and then break off to become new plants if they happen to land in a suitable place.

After leaving the cave we headed for Suardal to look at the great variety of ferns on the limestone pavement there, some of which I showed on 23 May.  We also found the liverwort shown on the right above, which I think is Preissia quadrata.  It is on limestone.

Ceterach officinarum   Polystichum lonchitis

Our main targets in Suardal were the Rustyback Fern (above left), in its only known Skye location, and the Holly Fern (above right), which grows in the same area, at a lower altitude than is usual for it.  We found both populations to be small but flourishing.

Viola riviniana leaf distortion   Neuroterus quercusbaccarum

Thiese strangely distorted Dog Violet leaves were noticed by one member of the party.  There were normal leaves on the same plant.  Finally, an Oak gall that I took a picture of at Ord before the start of the meeting.  This is the Autumn generation of the gall I showed on 12 May.  It is caused by the cynipid wasp Neuroterus quercusbaccarum.  The Spring galls are spherical and the autumn ones are disk-like.  Amazingly enough both have English names: the Spring one is called the Currant Gall and the Autumn one the Oak Spangle Gall.

Sun 19 Sep 2004

This morning the Pteridological expedition visited North Skye looking at horsetails.  We searched for Equisetum variegatum without success, but we did find Equisetum font-queri (shown here on 22 Jul) and Equisetum hyemale (shown here on 1 May).  It rained non-stop so no pics.  In the afternoon the others set off for the mainland to visit the gardens at Attadale.  It has rained incessantly all day and is forecast to do so all night and most of tomorrow.



All photos and other content copyright Carl Farmer