Placopsis lambii Hertel & V. Wirth

    Thallus placodioid, rosette-shaped, to 5 cm across, tightly appressed to the substratum, composed of lobes, rimose, confused towards the center, margins radially palmate and indented, bright, typically beige-pink, ochre-pink, brownish when dry, but possibly whitish with pink tinge, greyish, ochre pink, greyish, very pale grey-greenish when moist, upper surface occasionally dotted with rare and small globose cephalodia, distorted, not distinctly lobate, blackish, brown-blackish, brownish,  1-3 mm diam., but most often absent, soredia mostly numerous towards the center but occasionally distributed more or less in rings, greenish to greyish, 0.3-0.8 mm diam.. Apothecia sometimes numerous, sessile, 0.5-1.5 mm diam., disc flat, rough, pinkish to brown-reddish when dry, conspicuously pink when moist, thalline exciple very thick, concolourous to the thallus, transversally plicate. Ascii 8-spored, uniseriate, terete, weakly amyloid walls, 120-140 x 15- 18 µm (according to our own measures). Ascospores colourless, simple, ellipsoid, granular content, 14-18 (19) x 7-8 (10) µm (according to our own measures). Photobiont: thallus: Chlorococcoid; cephalodia: cyanobacteria. Thallus : C+ red, KC+ red. Rare and restricted to specific habitats: siliceous rocks and boulders, iron-enriched, moist stones and slates in slate or slate-schists quarries, also on stones among mine wastes of ancient lead mines. Formerly, in Finistère, this species was probably named Placopsis gelida since Placopsis lambii  has only been described in 1987. Nevertheless it may be difficult at the naked eyes to distinguish between the two species, because the descriptions of the latter are different according to authors, and also because of limited decisive differences:  thallus less bright, abundant cephalodia, lobate, brown, montane. Sometimes these taxa cannot be identified unless chemical spot tests are done, and consequently some authors consider that they are only chemotypes. Chemical spot tests have not been conducted on the specimen described here and we have taken into consideration the Wirth's description which fits perfectly: cephalodia rare, not lobate, apothecia numerous, on iron-enriched schists togtether with Lecidea lithophila in an area subjected to a climate under oceanic influence; our specimen have been collected in a sampling station were previously they had been identified by other skilled lichenologists. DNA markers on fresh samples presented here may be available in the near future and compared with samples from other European regions and US.

N.B. In drier and sunnier areas this species may appear as simple more or less isolated scales but always with greyish soralia, see: Placopsis lambii forma.

N.B. Frequent species in the rocky waste of iron or heavy metal mines (as is the case here) and then associated with Porpidia soredizodes and Rhizocarpon oederi.