LICHALP

Thelidium impressulum Zschacke

Lichenised.

Substrate: calciferous rocks

Altitudinal range: from the montane belt (potential vegetation: deciduous forests dominated by Fagus sylvatica and closed coniferous forests with Picea abies) to the alpine belt (potential vegetation: treeless Alpine grasslands and tundras, to the lower limit of perennial snow and the equilibrium line of glaciers)

Note: a species of the Th. pyrenophorum-group forming small, endolithic, whitish thalli and semi-immersed, small perithecia (to c. 0.2 mm in diam.) with involucrellum reaching down to the base, and ellipsoid, 1-septate, halonate ascospores (to 15 µm long); on calcareous rocks (dolomite at type locality) at mid-to high elevations; not rare in the Alps but probably regionally still undercollected.