Grimmia Hedw., Sp. Musc. Frond. 75. 1801.
Plants in dark-green or blackish green tufts or cushions, often hoary, mostly rupestral. Stems erect, forked or fastigiate branched, central strand usually present; rhizoids sparse. Leaves crowded, larger and more densely cluster at stem and branch tips, hygroscopic, imbricate, erect‑patent, crisped or spiraled, lanceolate, ovate‑lanceolate, plane, keeled or concave, gradually acute to acuminate; margins uni‑, bi‑, or multistratose, entire, plane or recurved on one or both sides; costa single, strong, subpercurrent to percurrent, flat or convex at back; upper cells mostly small and rounded‑quadrate, incrassate, often sinuose, smooth or rarely papillose, uni‑ to multistratose, basal cells quadrate, rectangular or thin‑ or thick‑walled, with straight or sinuose walls. Dioicous or autoicous. Setae short or long, straight or arcuate, twisted when dry. Capsules immersed, emergent or exserted, erect or curved, ovoid, oblong or cylindrical, smooth or ribbed when dry; stomata in neck; opercula straight or obliquely rostrate, mammillate or conic; peristome of 16 cuneiform teeth, rudimentary or absent. Calyptrae mitrate or cucullate, smooth, often lobed.