LICHEN: Peltigera praetextata in Cumbria

March 8, 2011:
Deciduous woodlands in Cumbria are the home to several species of lichen which are scarce elsewhere in England. Whilst searching for some of these yesterday, another more widespread lichen was seen and photographed. This was Peltigera praetextata Floerke ex Sommerf. which was growing on moss-covered boulders in woodland on the west side of Ullswater.


[Colour when dry; photo width = approx 10cm]

It is a relatively large 'leafy' lichen which anchors itself to the substrate by spike-like growths (rhizines) on its underside. The upper surface is brown to pale grey when dry but becomes dark grey or almost black when wet. The surface is bullate (i.e. it has raised vein) whilst the margins and surface cracks of older specimens can bear isidia (outgrowths containing its photosynthetic partner).


[Colour when wet. The isidia can be seen and also the bullate surface (in the lower part)]

This is the only relatively common British species of Peltigera which bears surface isidia. It is widespread and locally common on mossy boulders, tree-bases and on damp, heathy slopes.


[Showing the spike-like rhizines on the underside]

LICHEN: Peltigera leucophlebia near Haverthwaite, Cumbria

April 13, 2010:
This is a relatively large and quite striking lichen whose thallus is bright green when wet but becomes duller and browner if dried out.



In Britain it is quite local, often found in upland areas usually overgrowing bryophytes on base-rich substrates. However, photographed here it was in old coppiced woodland close to sea-level on small moss-covered limestone boulders.



Cephalodia (large dark spots) can be seen on the surface of the thallus. These contain a cyanobacterium capable of nitrogen fixation but the presence of any fertile apothecia is rare. Other characteristics are the curly (crisped) margins of the lobes of the thallus which has a white underside with black hairy rhizines.



Tightly crisped lobes are well in evidence



The black rhizines show up well against the white underside of the thallus.



I'm grateful to Jeremy Roberts and David Clarke for details of this locality.

LICHEN: Lobaria virens in Cumbria

April 7, 2008:
A visit to see this interesting lichen. Lobaria virens is an epiphyte which attaches itself to tree bark and whose presence is a classic indicator of ancient woodland. In the British Isles it has a westerly, oceanic distribution and is nowadays mainly found in south-west England, Cumbria, western Scotland, and Ireland. Everywhere however it is scarce or very scarce and is particularly susceptible to atmospheric pollution, especially sulphur dioxide.



It is found on the more acidic-barked trees such as oak and ash. When growing on trees which have become isolated due to woodland felling it may dry out and die off. Lobaria virens also occurs in Scandinavia and in western and southern Europe.



Below, the fruiting bodies (apothecia) can be seen as prominent, slightly concave brown discs.



Below, the small volcano-like protuberances are incipient apothecia which will develop similar to those shown above.



A Cumbrian oak with a large thallus of Lobaria virens. Towards the bottom left of the trunk the related Lobaria pulmonaria can just be seen.



I'm grateful to Mike Porter whose eagle-eye and persistence located the tree and both to him and to Jeremy Roberts for discussions about Lobaria virens.

LICHEN: Peltigera malacea, a scarce lichen

June 12, 2006
The lichen Peltigera malacea is very scarce in Britain where it's known from only three localities in Scotland, growing on oligotrophic soils amongst mosses, on acidic sand dunes and in conifer plantations on the coast. However, it is more frequent in Europe and it was seen and photographed in deep shade where on damp moss in the Styx ravine of Chelmos, a mountain in the Greek Peloponnese. Especially when wet, its thallus exhibits a striking bright green coloration.



The Styx ravine seen from near Zarouchla