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.
That is a real tester! Whilst the keels are convincingly arcuate, the leaves are very loose. The most convincing plants I've seen have all had quite strongly appressed leaves, but this is just my feeling and the only negative I can see. As for the gemmae, they had me convinced! What makes them algal? See what others say...
ReplyDeleteI've nothing constructive to add I'm afraid, just 'Not another Scapania to confuse me...!' Nice photos though.
ReplyDeleteI've been confused by gemmae/algae in the past too - not on Scapania, but an Orthotrichum lyellii (I thought) with capsules. Turned out to be another Orthotrichum with orange algae. So yes, how do you tell the difference?
Thanks for the comments.
ReplyDeleteAs for the 'gemmae' I was led by Jean Paton's comment that gemmae were 1 or two-celled and these are 3 or 4-celled (i.e. filamentous), like lots of algal colonies. However, had I looked closely at Jean's illustration of Scapania irrigua gemmae I would have noted that there is a filamentous stage. Presumably, the 2-celled gemmae are 'budded off' like yeast cells. Also the photo here is similar to photos of Scapania irrigua gemmae posted on line. Lesson learned!
I take Barry's point. Despite the very distinctive semicircular keels the balance may be tipping in favour of Scapania irrigua. I've amended the post.
I think the gemmae of Scapania paludicola would look more obviously dark than these, but this is one of the most convincing pieces of mimicry I've seen in this apparently unrelated species pair. I do wish somebody would DNA test a suite of Scapania irrigua var 'pseudopaludicola' specimens along with obvious classic S irrigua and obvious gemmiferous mire S paludicola!
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