I spent my lunch hour (well actually a split 20 minutes before and after my main work) recording in SN90F, east of the A4061 between Treherbert and Craig y Llyn. This was slightly pointless because there were already over 70 species recorded from the tetrad, but it looked like good ground as I drove past and I thought I'd add something. In the end I found about 95 species, and there were 14 on the previous list that I didn't see (mostly plantation & track species), so the tetrad is now nicely over the 100 mark and can probably be regarded as 'done'.
First stop was a small, sealed-up, graffiti-covered building surrounded by sculptures, where I recorded various ruderals including Tortella tortuosa, Orthotrichum cupulatum and Schistidium apocarpum on concrete. A yomp up through scree with 4 cushions of Scapania gracilis led to the Cwar Du cliff base at 450m altitude, where Ditrichum zonatum new for Glamorgan awaited me. Nearby were Campylopus atrovirens, a small form of Gymnocolea inflata, some Lophozia sudetica, and a bit of Rhabdoweisia crispata. A rowan added Cololejeunea minutissima and other common epiphytes to the list.
After I'd finished my work near Glyncorrwg I stopped briefly at Nant y Bwlch, just down from Cwar Du, to add some stream mosses to the list. Hygrohypnum ochraceum and Hyocomium armoricum were present in the stream, Ptychomitrium polyphyllum was on boulders, Polytrichum alpinum was on a low cliff, and slight base enrichment was indicated by a few shoots of Trichostomum brachydontium among Amphidium mougeotii. Perhaps the highlight of this area was some Lophozia bicrenata with perianths on humus under heather - a thoroughly unpredictable species.
So, a worthwhile stop given that I didn't have time to properly bash an unknown tetrad.