Lichens marins - Circinaria contorta (Hoffm.) A. Nordin, Savic & Tibell = Aspicilia contorta (Hoffm.) Kremp. subsp. contorta

    Thallus crustose formed of areoles with rounded angles scattered on the substratum and generally separated from each other, smooth surface, rounded and convex, dirty whitish, gray-greenish, greyish if dry, glaucous green if moist, no hypothallus except sometimes between the areoles grouped together in the middle of the thallus but not at the periphery. Apothecia 0.2-0.6 mm in diameter, usually only one per areola, of which it can then occupy almost the entire surface giving the appearance of a volcano, rarely 2 or 3, disc flat, blackish but covered with a bluish or green-blue pruine, raised margin often radiantly striped. Spores broadly elliptical to subglobose, simple, colorless, 4 per ascus but sometimes 2 or 6 (see Aspicilia contorta 6-spored ascus), 18-28 x 17-24 µm. Photobiont: Chlorococcales. C-, K-, P-. Common species on non- or low-acidic substratum: hard limestone blocks, walls, concrete, cement, pavement tar where this species takes on the appearance of old chewing gum stains. See Aspicilia contorta subsp. hoffmanniana quite similar but whose areolas more or less flat have a rugose surface, are more angular, more grouped and tight against each other.

This species, a little nitrophilic, is very variable and we can separate several forms (linked by intermediaries) depending on the substratum and exposure to the sun:

Aspicilia contorta subsp. contorta forme des substrats humides et peu ensoleillés.
     This form is characterized by its appearance on damp substrates and in the shade, its colorations are greenish permanently, even in dry weather.

Aspicilia contorta subsp. contorma forme des substrats secs et ensoleillés.
     This xeric, thermophilic form is characterized by its appearance on dry and sunny substratum, its colorations are more or less brownish depending on the amount of sunlight.