Up the Afon Wern

The head of the Afon Wern, on the south side of Mynydd Preseli

Yesterday's mission was to try to add Bryum riparium to the Pembrokeshire list, so I headed for the most obvious upland stream in the county, the Afon Wern on the southern flank of Mynydd Preseli. A farmer offered me a quad bike ride up the hill, but I opted to wade the stream up from the road instead. Typical riparian mosses here included Fissidens bryoides var. cespitans, Hygrohypnum ochraceum, Racomitrium aciculare and Fontinalis squamosa.  

Fissidens bryoides var. cespitans

A new VC record came in the form of Ulota drummondii, a few tufts of which were fruiting on the twigs of a streamside gorse bush. The orangey leaves and bright white peristome teeth are distinctive. An eroding vertical acidic clay and stone bank nearby had common calcifuge bryophytes such as Ditrichum heteromallum, Pogonatum aloides and Solenostoma gracillimum, together with fruiting Dicranella subulata.

Ulota drummondii peristome and location photo

When I reached the steep headwater section, most rocks became dominated by a luxuriant growth of Marsupella emarginata var. aquatica, together with smaller patches of Nardia compressa in places. Concentrating on the vertical rock faces alongside cascades was more productive though, yielding a new liverwort for the county in the form of a tiny patch of Hygrobiella laxifolia. Although a few juvenile Marsupella shoots were mixed in, under a microscope the large underleaves, purple rhizoids and lack of oil bodies in the cells were all visible. More widespread species on these rocks included Trichostomum tenuirostre, Campylopus atrovirens and Blindia acuta. I collected five shoots of a small Fissidens in the optimistic hope that it might be the non-British F. jansenii rather than F. pusillus, but although the leaf apex looks promising, the tiny fragile leaves have proved beyond my sectioning abilities and I've shredded two shoots already. I'll leave the last three for Tom.....(unsurprisingly, he determined this as pusillus) 

Hygrobiella underleaves and habitat photo

The sun came out, and there was just time for one last find before the hike back - the target Bryum riparium, a few patches of which were on stream edge rocks. Confirmation under the microscope came in the form of the funky rhizoidal gemmae, pictured below.  A three NVCR day - I don't think I've had one of those before!

Bryum riparium