Porella arboris-vitae revisited

I was working on Old Castle Down this morning, and couldn't resist a quick stop to admire the fine patch of Porella arboris-vitae which grows on a lump of limestone here (spot the Mottled Grey resting on the same rock).

I was pleased to find a couple of additional patches of the Porella on adjacent rocks (highlighted in photo below - the original patch is on the right). Somehow I'd missed these on previous visits.

I also checked a nearby limestone wall, but although it was wonderfully mossy, including big sheets of Porella platyphylla, I couldn't find any more arboris-vitae.

Old Castle Down comes up trumps again

I chanced across a patch of Porella arboris-vitae during a site inspection at Old Castle Down this afternoon. What a super looking liverwort. I wasn't really looking for bryos but the dark patch on a pale limestone background (see lower photo) attracted attention immediately.

The funny thing is that a year ago I did some habitat surveys (including quadrats) about 20m away, and we even had lunch in the grassy area behind the rock in the photo. I didn't spot it then as the patch is on the shady side of the rock facing the woodland edge. I only saw it today as I made a quick inspection of oak buds for Purple Hairstreak eggs.

There didn't seem to be any doubt about the ID but I took a small sample home and nibbled a tiny fragment. This was about an hour ago and the tip of my tongue is still numb - it makes Water-pepper seem quite mild in comparison!

Looking at the Atlas, the nearest Welsh population would appear to be about 50km away. There are closer populations on Exmoor though (just like the High Brown Fritillary!).

Radnorshire riches

A couple of years ago I stopped for a lunchtime walk on Aberedw Rocks SE of Builth Wells, and found a rock covered with Grimmia laevigata and another with abundant G. decipiens.  Both were new to the site, and they suggested that it could be a very rich area for saxicolous mosses.  Targionia hypophylla has been known there for several decades, and there is an intriguing 20th century record of Bartramia stricta from the site, which was purged at the same time as one from Pembrokeshire [so effectively that I couldn't find out where the Pembs claim was made].

Since then the site has been on my 'to do' list, and a sunny 27th April seemed ideal.  I didn't find B. stricta or any more of either Grimmia, but there were several other good species present, including Marchesinia mackaii (photo), Bartramia ithyphylla, Pohlia cruda, Frullania fragilifolia, Seligeria recurvata, Plagiochila bifaria, P punctata & P spinulosa, Porella arboris-vitae (photo) and Orthothecium intricatum.

The two rarest species were the Nationally Scarce Plagiopus oederianus (photo, with some Bartramia pomiformis for comparison), which is abundant on north-facing rock outcrops, and the Nationally Scarce Encalypta ciliata (photo), which was only present in one small area and was last recorded on the site in 1923.

Biggest surprise was a tuft of Orthotrichum rupestre (photo), which only has 3 previous Radnorshire records and remains unknown further SW in Wales.  Its very hairy calyptra, superficial stomata, upright exostome teeth and half-pliccate capsules were distinctive.

I thought that the highlight of the day was going to be a round-leaved liverwort in a flush, which clearly wasn't Odontoschisma and seemed sure to be my first ever Jamesoniella undulifolia.  To my shock and disappointment, I found under the microscope that it had violet rhizoids, making it Jungermannia hyalina very out of habitat.

Overall it was a wonderful day of mossing, and the site is clearly of SSSI quality for its bryophytes.