This is Rhaeadr Ddu - the most spectacular waterfall on the Afon Gamlan in Coed Ganllwyd NNR, Meirionydd. A recent survey by Des Callaghan has helped to confirm this woodland as the richest for oceanic bryophytes in Wales and the site with the largest Welsh populations of a large number of species such as Cephalozia catenulata and Sematophyllum demissum. Des did not refind the Nationally Scarce, Section 42 Paraleptodontium recurvifolium there, and nor has anyone since 1958. I spent half an hour today searching specifically for it and found none, though it is just possible that an abseil survey might reveal it. Its loss is a sad tale of thankfully bygone days:
Last month I looked at all of the Welsh specimens of Paraleptodontium in the NMW herbarium, just to confirm that the species really was historically present at 10 or so Welsh sites. All were correctly identified and all were depressingly, grotesquely large. Between 1900 and 1958 the colony at Coed Ganllwyd was plundered for private collections and for 'distribution' to other bryologists and herbaria repeatedly, and there are more than 25 specimens from the site. Many of these are 10x20cm pure patches, suggesting that bygone bryologists grabbed good handfuls of this rare species. The last collection is from 1958, and its collection (by a now deceased bryologist who I will not name here) horrified Derek Ratcliffe who witnessed the event. The collector actually said it was the last bit that he could find on the site!
Most of the specimens of Paraleptodontium from Rhaedr Ddu contain bits of Breutelia chrysocoma and/or Sphagnum denticulatum, and the 1958 specimen says "growing through Campylopus setifolius opposite the main waterfall". As I had seen C. setifolius there on previous visits I knew just where to look, so I had a glimmer of hope that Paraleptodontium could have survived; it hasn't. The associates are all still there and look spectacular, especially the large patches of the Campylopus.
Despite this loss, Coed Ganllwyd is the most wonderful place in which to see oceanic bryophytes - take a hand lens and the Field Guide (and even better a bryologist who can show you what's there) and admire boulders and rockfaces covered with Sematophyllum, Drepanolejeunea, Harpalejeunea, Colura, Adelanthus, 6 species of Plagiochila, Hypnum callichroum, Dicranodontium denudatum etc. etc. It is just a 5 minute walk from the National Trust carpark at Dolmelynllyn, Ganllwyd. Just please don't collect any specimens!