Friday, March 07, 2014

River Gorge and Filmy Ferns

No takers this week for my planned walk so I found my way to my first sighting in the UK of Filmy Ferns alone up the River Nedd Fechan from the Pont Melin Car park. It will be easier going later in the year I hope and there will be more to see - so I do hope to go back - but accessing the well-recorded site for Hymenophyllum species wasn't difficult.
Hymenophyllum wilsonii on a cliff near the Nedd Fechan
and closer

Now I need to start spotting them in new sites to justify my role !

I have always delighted in finding and examining these in Western Ireland so it was good to do the same here - even if the ground under foot was rather mobile after the recent rain - making examining with a hand lens interesting. Also I find I am more and more uncertain about the exact species the more I investigate these - and I suspect there are hybrids where they occur together. (Hybrids have relatively recently been found by proper botanists in Cumbria.)

Hymenophyllum tunbrigense

These ferns are fascinating because amongst other things they have very thin leaf blades one cell thick - and the cells are quite large as this picture shows (click on it to see full size):
This picture also shows the characteristic toothed sorusof  Hymenophyllum tunbrigense which makes identification of this species easy enough when they are present.

They demand high humidity and cannot survive drought for long but I've found they also don't seem to grow in the dripping wet areas either like this tufa outcrop I passed on the way:
So north facing, near running water and as often as not on a vertical rock face it seems. 

I explored further up the river, increasing my species count slowly as I went but wasn't able to access the river edge at all points. Certainly I didn't manage to find any more Hymenophyllum - even if I was momentarily confused by a non-vascular similar:
Plagiomnium undulatum I think

It made me realise I'm not as solid on the differences between the Bryophytes and Vascular Plants as I should be - this seemed to have a leaf vein - but no, consulting my Penguin Dictionary of Botany I discover that is a "nerve" and consists of a "narrow thickened strip of tissue down the middle of a moss leaf". The vascular plants have differentiated veins and are altogether much more sophisticated in their ability to move water around. (Even if the filmy ferns are still pretty fragile with respect to coping with drought.)

There were many other interesting sights along the way including this Pellia species (?) in fruiting mode - spores came away in a cloud when I touched a "ripe" fruiting body as below.
Some more pictures:

And finally I stopped off at Maen Llia on the way back...

No comments: