Acarospora hellbomii H. Magn.

Bot. Notiser: 232, 1926.
Synonyms: Acarospora marcii H. Magn.
Distribution: N - TAA (B 189317), VA (B-189320). C - Sar.
Description: Thallus crustose, episubstratic, dark reddish brown, epruinose, areolate-subsquamulose. Areoles 0.5-1 mm wide, dispersed, angular, irregular in shape but not lobed, broadly attached, the lower surface (along the margins) dark-coloured. Cortex 12-25 µm thick, the cortical cells 1.5-2 µm wide, overlain with an amorphous layer; algal layer continuous; medulla 80-120 µm thick. Apothecia lecanorine, immersed in the areoles, 2-3(-5) per areole or sometimes solitary, 0.2-0.4 mm across, with a strongly concave, then more or less flat, rough, epruinose disc. Excipulum distinct, c. 10 µm thick, I+ blue; epithecium brown; hymenium colourless, 90-100 µm high, I+ blue; paraphyses coherent, c. 1.5 µm thick, the apical cells subcapitate, 3-4 µm wide; hypothecium greyish, 30-50 µm high. Asci c. 200-spored, clavate, the apical dome K/I-. Ascospores 1-celled, hyaline, narrowly ellipsoid, 3-5 x 1.5-1.7 µm. Photobiont chlorococcoid. Spot tests: thallus and medulla K-, C+ red, KC+ red, P-. Chemistry: gyrophoric acid.
Note: on exposed surfaces of iron-rich siliceous rocks in eutrophicated situations. A poorly-known taxon based on a type from extra-alpine SW Europe.
Growth form: Crustose
Substrata: rocks
Photobiont: green algae other than Trentepohlia
Reproductive strategy: mainly sexual
Species of metal-rich rocks

Commonnes-rarity: (info)

Alpine belt: very rare
Subalpine belt: very rare
Oromediterranean belt: very rare
Montane belt: very rare
Submediterranean belt: absent
Padanian area: absent
Humid submediterranean belt: absent
Humid mediterranean belt: absent
Dry mediterranean belt: absent


pH of the substrata:

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Solar irradiation:

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Aridity:

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Eutrophication:

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Poleotolerance:

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Altitudinal distribution:

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