Thelopsis rubella Nyl.

      Thallus crustose, well applied to its substrate, thin and poorly defined, humid: gray-greenish, dirty grayish if dry (and then from a distance with  Schismatomma decolorans appearance so devoid of perithecia!). Perithecia few in number, scattered all over the thallus, visible only in winter and spring because they are highly evolving and therefore very variable, at the beginning soft, gelatinous and buried in the thallus then emerging in a small dome with a ring of the remains at the base thallus, 0.3-0.6 mm in diameter, assuming a "nipple" appearance (as the name of the genus suggests), reddish-brown, pinkish-brown, orange-brown, becoming brownish or blackish-brown in drying and finally disappearing at the end. Asci in the form of very elongated sacs ending in a point, 130-150 x 15-25 µm according to our measurements, containing up to a hundred spores. Colorless spores, largely elliptical with rounded ends (pharmaceutical capsule-shaped), 3 times septate, 9-12 (15) x 4-5 (6) µm according to our measurements (NB become, if they are well ripe, gray- bluish in diluted Lugol). Photobiont: Trentepohlia. Negative colored chemical reactions. Species occurring on the rough, more or less altered bark of the base of old trees in humid forests (in the area of ​​the hepatic Metzgeria furcata). This species goes unnoticed in summer or fall when it is usually devoid of perithecia. Watch out for Strigula thelopsidoides with red-orange perithecia, which has pycnidia and whose spores are 8 per ascus.