Diploschistes muscorum (Scop.) R. Sant.

   Thallus spread out on the soil, up to 5 cm diam., soft when moist, crumbly if dry, weakly areolate, the surface uneven, ± coarsely verrucose, scabrid not pruinose, whitish, white to dull grey like the prothallus, more or less visible. Apothecia urceolate,  1-2 mm diam., disc flat, black, ± densely white-pruinose turning to grey, thalline margin rather thick, slightly or not striated. Ascospores muriform, with 5 transverse and 1-2 longitudinal septa, 25-35 x 10-15 µm according to literature, 27-32 x 12-14 µm according to our measurements. Photobiont : Trebouxia. C+ red, K- or K+ yellow or red, KC+ red. On well-lit calcareous dunes, dry and mossy. Rare in our prospection area.

      Diploschistes muscorum initially parasitizes the squamules of Cladonia sp. and in particular of Cladonia pocillum, or of Cladonia rangiformis and according to our observations probably also of Squamarina cartilaginea which share its habitat. The mycelium of the fungus settles on the host's squamules and uses its photobiont: Trebouxia irregularis, it can even make apothecia on the squamules. When the host is destroyed it forms an independent thallus but with another photobiont: Trebouxia showmanii. See the photographs on the file of Diploschistes muscorum parasite de Cladonia pocillum, Diploschistes muscorum parasite de Cladonia rangiformis and Diploschistes muscorum parasite de Squamarina cartilaginea.

   For more details see: Friedl T. 1987. Thallus development and phycobionts of the parasitic lichen Diploschistes muscorum. The lichenologist. 19: pp. 183-191.