As with other lichens in the Pannariaceae this species with cyanobacteria as the photosynthetic partner usually has a distinctive blue-black rim to the thallus (called the hypothallus). It, however, barely extends out from the edge of the thallus in this species. The centre of the thallus consists of chestnut to grey brown lobes that become quite elongate towards the edge. These squamules break down to initially form similarly coloured knob-like soralia that in turn develop into extensive patches of blue-grey soredia that can cover most of the thallus. When fresh and moist it can be separated from most other species by its distinctive hospital disinfectant smell. P. triptophylla has more elongate isidia and smaller marginal squamules. Fuscopannaria sampaiana has cream-coloured soralia (not blue-green). (RGW)
Photo: Ray Woods
It occurs on the basic bark of trees in moist, sheltered and unpolluted woodlands and occasionally on silty boulders in mountain streams (Pentecost (1987)).
We know little of the detailed distribution and population sizes of this species in Wales. It is threatened by acidic atmospheric pollutants, the loss of host trees by felling and natural collapse and a lack of nearby suitable host trees onto which to expand. The complete cessation of grazing in some sites may lead to its loss through being shaded out by dense evergreens such as ivy, holly and rhododendron. It is accorded a threat status of vulnerable in Wales though a better understanding of its population size and trends in abundance might indicate that endangered is a more realistic status. In Britain it is considered to be near threatened. British populations are considered to be of international importance. (RGW)