Dark brown speck lichen

Verrucaria nigrescens is a widespread species of crustose lichen in the family Verrucariaceae. It was first formally described as a new species by Christiaan Hendrik Persoon in 1795. The lichen produces a very dark brown thallus that grows on rocks; the medulla is black. There are black perithecia that resemble buried dots, and which measure 0.15–0.3 mm in diameter. Ascospores measure 14–24 by 7–11 μm.