A Last Crack at Castlemartin

It’s all gone a bit cold and dry for fieldwork, but I had one last crack at the Castlemartin Range yesterday. 

A patch of fruiting Pottiopsis caespitosa on a second sheep-walk across Linney Burrows was nice, and perhaps less typical than the trackside locations elsewhere on Range West. Fossombronia incurva here was also good to find - I've seen it in sand quarries and sand-schools for horses, but not in a 'natural' sand habitat. Didymodon acutus was also in a few places on the dunes - it's proven to be widespread and sometimes abundant on tracksides across the Range. The Atlas suggests that most previous records of the Nationally Scarce Didymodon acutus have proven to be D. icmadophilus on closer inspection. Sharon Pilkington looked at a few samples, and found one of them to be genuine acutus, with smooth rather than papillose cells, distinctly thicker-walled and with more rounded lumens. It is also more yellow brown, rather than the dark green of icmadophilus, and the nerve is not as long excurrent. There are only a handful of records of this species from the south of England, and the Castlemartin record is the first for Wales.

Didymodon acutus on limestone track

A few scattered shoots of Microbryum floerkeranum on a target gully on Flimston Down also had late-ripening capsules.  A good find alongside was a small patch of Bryum gemmiluscens, which looks as if it might be new to Wales. Compared to the common Bryum dichotomum, the bulbils in the leaf axils are yellow and only have very small, rudimentary leaf primordia.

Bryum gemmilucens

Bulbil from leaf axil of Bryum gemmilucens

Elsewhere, I found some Cephaloziella dentata in a third location, but with the range now mob-stocked with sheep, and a film of algae coating many of the barer areas within the heath, monitoring the population is a near impossible task. I like the small bryophytes, but the gemmae-covered shoot tips emerging from the algal mat aren't much bigger than a grain of sand, and my knees are a bit sore at the moment.....