A rare lichen in Cumbria: Peltigera collina

February 26, 2013:

A rare forecast for good weather resulted in a hurriedly planned visit to the Seathwaite valley (Borrowdale, Cumbria) in the hope of finding and photographing Peltigera collina. In England this is a very scarce and local lichen and in Cumbria is restricted to growing on the trunks of a few ancient pollarded ash trees.

Peltigera collina (top two photos) and a pollarded ash (above) which had various other interesting and local lichens growing on the mossy lower part of its trunk. The marginal soredia can be seen in the centre photograph

In the beautiful warm summer-like weather P collina was soon located, low down near the base of just such a pollarded ash, although intermixed with three other species of Peltigera as well as Lobaria virens. Initially, this led to some confusion in identification but P. collina can be unequivocally distinguished from other British members of the genus in bearing clusters of soredia along the margins of its small neat upturned lobes. However even this was not completely straightforward because the neighbouring P. praetextata (see below) bore small isidia and folioles giving it a superficially similar appearance.

Peltigera praetextata, the marginal isidia and folioles can be seen in the lower photogrph

P. collina is a component of the 'Lobarion' association of lichens, a specific indicater and component of mild oceanic ancient woodlands. It occurs rather more frequently in north-west Scotland.

Peltigera horizontalis (sterile thallus)

Peltigera horizontalis

Lobaria virens

Seathwaite valley

                                                                                                                                                                          

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]