Graig Fawr, RCT

Graig Fawr

Yesterday afternoon, H and I did our weekly square-bashing trip to RCT. We decided to have a look at Graig Fawr, an imposing cirque that overlooks Treorchy in Rhondda Cynon Taff. Old vascular plant records, which list Beech Fern, Oak Fern, Parsley Fern and Wilson's Filmy-fern, suggest that, like Craig y Llyn, it is a refuge for Boreal-montane species. Setting out from a very convenient lay-by on the A4061, we took a track that runs below Graig Fach. A large clump of Neckera crispa draped over a concrete culvert was a good start.

Neckera crispa on concrete culvert below Graig Fach

Access to ledges on Graig Fach and Graig Fawr is difficult and it will take quite an effort to survey this site properly. On the day we took some easier options, firstly checking the lower scree and then climbing into an inviting gully. Below the gully, scree was covered in the usual Racomitriums (aquaticum, ericoides, fasciculare, heterostichum, lanuginosum) and Andrea rothii ssp. falcata, but the gully itself looked more promising.

Gully bisecting the southern edge of Graig Fawr

We noticed a small amount of Hymenophyllum wilsonii on the north-facing wall of the gully and a large population of Huperzia selago, with some individuals as big as dinner plates. These must be of significant age (many decades) and the fact that H. selago is not listed in old records suggests that this gully may not have been visited by many botanists for a long time.

Huperzia selago in gully

This was also suggested by some of the relatively common bryophytes we recorded there which were not in the MM database for this tetrad (SS99H); e.g. Amphidium mougeotii, Batramia pomiformis, Campylopus atrovirens, Hookeria lucens, Hyocomium armoricum, Marsupella emarginata var. aquatica, Palustriella commutata, Plagiothecium denticulatum, Riccardia multifida.

 Marsupella emarginata var. aquatica in gully stream

It was very cold in the gully and persistent hailstones didn't help to maintain our enthusiasm. But towards the top of the gully in the vicinity of SS92709562, in a dim, humid overhang, we found a Rhabdoweisia sp.

 Rhabdoweisia crenulata in humid overhang, Graig Fawr (RCT)

It's good to have Barry's recent photos of R. crispata (Tan-y-Graig) for comparison. The Graig Fawr Rhabdoweisia differs from the Tan-y-Graig plants in a number of ways. Firstly they have larger leaf cells (16-24 microns). Secondly, the mature leaves are relatively broad (usually > 10 cells wide either side of the costa). Thirdly the upper leaf margin has noticeable, large, protruding (often multicellular) teeth.

 Wide leaf tip of Graig Fawr Rhabdoweisia crenulata showing prominent teeth

Multicellular teeth of Graig Fawr Rhabdoweisia crenulata

This looks like Rabdoweisia crenulata (Greater Streak-moss) to me, which was recoded once before in VC41 by Tony Smith (Craig y Llyn in 1961). As always, comments and corrections will be appreciated.

Exploring RCT is time consuming and requires a fair amount of effort, but the rewards are obvious. There's lots of crags and cirques and a substantial amount of conifer forest. Goodness only knows what is lurking on some of those ledges! Our records yesterday bring the total for SS99H up to 75.

Marsupella emarginata

Marsupella marginata habitat, Corrwg Fechan Valley

Minimal torment here, and a species that all of you know well, but a nice record of it in one of the headstream cwms of the Afan Valley, near Glyncorrwg. The habitat is a dripping wet, north-facing sandstone rock face where it grows in a small area as pendant mats with Pellia epiphylla, Hyocomium armoricum and Diplophyllum albicans. Drier areas of rock face in the vicinity are plastered with Amphidium mougeotii.

It looks like var. aquatica to me, which is also found at Craig y Llyn (not far away as the crow flies).

The leaves have a very shallow notch, the shoots are relatively large and the habitat is right for var. aquatica. Apparently there can be some overlap between var. emarginata and var. aquatica.

Marsupella emarginata leaves with recurved margins

Under the microscope the recurved leaf margins, which confirm M. emarginata, are easy to see.
 Watson's description draws attention to the rounded cell lumen and the the well-developed trigones, which can be seen in the photo below.

I'm not sure to what extent other Marsupella spp. show such a thick-walled cell structure. Perhaps Sam or Graham can comment on that.

Craig y Llyn

A few extra photos from our visit to the cliffs above Llayn Fach on the 10th October, a short account of which appears HERE.

Blindia acuta (Sharp-leaved Blindia)

Fissidens osmundoides (Purple-stalked Pocket-moss)

Marsupella emarginata var. emarginata (Notched Rustwort)

Marsupella emarginata var. aquatica (Robust Rustwort)

Nardia compressa (Compressed Flapwort)

Scapania gracilis (Western Earwort)