Umbilicaria polyrrhiza (L.) Fr.
Thallus foliose, forming rosette, 3-8 cm diam., lobes intertwined and frequently overlaping, margins folded down, wavy to curly, indented, allowing black rhizines to be seen, upper surface smooth to slightly irregular and verrucose, copper-brown, brownish, chocolate, lower surface blackish with a black compact and densely felted layer of often branched rhizines (or best, rhizinomorphs). Apothecia very rare, 1-2 mm diam., black, not gyrose but with radiating gyri from a central point, exciple soon excluded and seldom visible. Ascospores simple, hyaline, ellipsoid, 8-9 x 3-6 µm. Photobiont: chlorococcoid. Medulla : C+ red, K-, KC-, Pd-. Montane trends, grows on highly exposed siliceous rocks of ridges in hills and mountains. Uncommon in our prospection area and limited to the Arrée Mounts. See Umbilicaria polyphylla of which the lower surface is devoid of rhizines. N.B. The specimen of Umbilicaria polyrrhiza, presented here were collected in an area well known of the Breton lichenologits, but in fact may apply to a morph of Umbilicaria polyphylla with a few rhizinomorphs on the lower face, not extending beyond the margin; typical specimen photographed in Sweeden are also presented for information. Not to be confused with old speciment of Lasallia pustulata of which the lobes are bloated and with isidiate margins.*