Thallus thin, 26–65 µm thick, subgelatinous, translucent when fresh and wet, smooth, ± matt or slightly glossy, continuous, grey-green to mid brown, contiguous conspecific thalli not separated by dark lines. Cells irregularly arranged or in weakly defined columns, coherent, without air spaces between the cells. Cortex poorly differentiated, comprising a thin layer with few or no photobiont cells, cortical pigment, when present, brown; without a dark basal layer.
Anamorph: not known.
Teleomorph: ascomata perithecia, forming conic-hemispherical mounds 400–600 µm diam., at first covered by the thallus up to the apex, later sometimes eroded to expose the black ostiolar region. Ascomata 250–310 µm diam. Involucrellum conical, reaching to the substratum, dark brown, K+ dark grey. Interascal tissue absent, periphyses 20–45 µm long. Asci clavate, I–, fissitunicate, the wall thickened above, ocular chamber usually present; dehiscence by extrusion of an endotunica to form a delicate rostrum, 8-spored. Ascospores arranged biseriately, (19–) 21.5–26.5 (–30.5) x (8–) 9–10.5 (–12) µm, length/breadth ratio (2.0–) 2.2–2.7 (–3.0), ellipsoidal, hyaline, aseptate, with a perispore that apparently degenerates with maturity of the spores.
Not formally assessed. Rarely encountered to date, but widely distributed in northern and central Europe, perhaps indicating that it is under-recorded rather than genuinely rare.
Verrucaria placida differs from V. hydrophila in the larger, less crowded perithecia and larger ascospores. However, V. placida is more likely to be confused with V. andesiatica (sensu Orange et al. 2009), which is morphologically similar but not closely related. That species differs in the wider ascospores; in addition, pycnidia are sometimes present, adjacent thalli may be separated by dark lines, the thallus is typically even smoother and more glossy, and the perithecia are usually a little less densely spaced.
In GB&I, recorded from several sites in VC43 Radnorshire. Also reported from Norway and southern Germany.
On shaded siliceous rocks and stones in small streams in woodland.