Catillaria nigroclavata (Nyl.) Schuler

     Thallus crustose, thin and sometimes inconspicuous, smooth to rough, gray-brownish, pale brownish, olive, ... sometimes greenish by algae or cyanobacteria. Apothecia very small, sessile, 0.1-0.3 mm in diameter, disc flat, dark brown, blackish, black, margin clearly visible, blackish, black. Colorless ascospores, elliptical, (0)-1-septate, 8-10 x (2) 2.5 (4) µm according to the literature, 7-10 x 2-3.5 µm according to our measurements. Paraphyses typically terminated in a large black bulge. Rare pycnidia. No colored chemical reactions. Discreet and inconspicuous species occurring on the bark of deciduous trees in humid forests. Easy to confuse in the field with Amandinea punctata but the latter species has larger, rounded apothecia and a different microscopy and with Catillaria chalybeia but the latter species very rarely occurs on the bark.