This flush, which drains water off reclaimed open cast slopes on to a forest road dressed with calcareous chippings, is dominated by Sarmenthypnum exannulatum. Other associates include Calliergonella cuspidata, Philonotis fontana and Sphagnum subnitens, all indicative of a neutral flush.
Sarmenthypnum exannulatum, Nant y Cafn
Sarmenthypnum exannulatum,Nant y Cafn: distinctive long, curved alar cells at leaf base
We also noted a Scapania scattered among the Philonotis which looked promising for S. paludicola. However, given the frequent occurrence of S. irrigua on forest roads and the difficulties in separating these two in wet habitats, I knew caution was required, particularly in view of comments that Sam has made on this blog with respect to the S. paludicola/irrigua in Pembs. The preponderance of almost semicircular keels on examined specimens did suggest S. paludicola. I thought I could see gemmae on some shoots, so some specimens were taken for examination. Jean Paton describes the gemmae of S. paludicola as 'green but soon becoming yellowish brown or brown to brownish red or pink to purplish red'. Those of S. irrigua she describes as green. Generally speaking you should expect to see darker pigmented gemmae on S. paludicola (if they are present). Here are some photos:
Scapania (c.f. paludicola), Nant y Cafn, with preponderance of arcuate keels
The occurrence of this Scapania with Sarmenthypnum exannulatum is certainly consistent with it being S. paludicola, but I am not familiar enough with this species to be certain. It would be a second record for NPT and an interesting addition to the bryoflora of forest roads in south Wales. Comments welcome.