Saturday May 31st 2014

Arthur’s Seat, Edinburgh

Led by: Mary Gibby

In attendance: Mary Gibby, Frank McGavigan, Hannah Mulcahy, Peter Upton (plus family), Stuart Maxwell, Celina Barroca, Gillian Little, Nicole Brandon and Chris Nicholson.

It was a glorious sunny day, perfect for ferning. Mary Gibby led the field trip up Arthur’s Seat, our BPS ranks swelled by enthusiastic RBGE MSc students, an RSPB representative, and the local Recorder for Edinburgh.

We headed up the path opposite the Holyrood car park on Queen’s Drive to Hunter’s Bog and very soon encountered the first of our targets for the day, the Adder’s tongue fern, Ophioglossum vulgatum. [NT27287348 & NT27317343]. After the first one had been pointed out it became slightly easier to spot other specimens growing in the damp grass on either side of the path. Mary explained the structure of the fertile spikes, pointing out the ridges where locules are, which were visible with a hand lens. I did not know that the genus Ophioglossum has the highest chromosome count of any living organism.

Also growing nearby we saw Equisetum arvense, E. palustre, E. fluviatile and E. × litorale, a hybrid between E. arvense and E. fluviatile. Amongst the grasses and ferns were numerous Northern Marsh Orchids, Dactylorhiza purpurella.

Moving further up the valley, a narrow ditch held examples of Dryopteris dilatata and provided the opportunity, a necessary component of any BPS Scottish field trip, to puzzle over Dryopteris affinis agg.. We recorded D. cambrensis and D. borreri. Some splendid stands of D. filix-mas against a backdrop of gorse in blazing bloom provided a good spot for a group photo.

We then walked over to the south side of Arthur’s seat where the road hugs the base of the cliffs. As we walked along the footpath by the side of the road we saw, on the north side of the wall that bordered the path, examples of Polypodium vulgare, Asplenium trichomanes subsp. quadrivalens, A. adiantum-nigrum, A ruta-muraria and A. scolopendrium.

The cliffs, on the north side of the road, are south facing, warm, slightly basic basalt rock. It was here that Mary showed us what was for me the highlight of the day – sizeable clumps of A. septentrionale and a single plant of A. x murbeckii. A. x murbeckii is a hybrid between A. ruta-muraria and A. septentrionale. Mary has been monitoring the clump for a number of years. It has remained stable in size and the only confirmed example of the hybrid in this location. Also present on the cliffs were Polypodium interjectum, A. adiantum-nigrum, A. ruta-muraria and A. trichomanes subsp. quadrivalens.

As we headed back down the path Stuart Maxwell, the local Recorder spotted something exciting we had missed on the way up – a plant of A. septentrionale growing in the wall amongst A. ruta-muraria – a shadier, cooler location than the plants of A. septentrionale enjoy on the cliffs. That was not all, intriguingly, nearby, Stuart found what may be the hybrid.

A possible new discovery of A. x murbeckii
A possible new discovery of A. x murbeckii
Formal identification will be needed to confirm whether a second plant of A. x murbeckii has been discovered on Arthur’s Seat.

Chris Nicholson

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