Grimmia

Grimmia is a genus of mosses belonging to the family Grimmiaceae. These mosses are typically found in exposed, rocky habitats, often on dry, north-facing rock surfaces or cliff faces. They are characterized by their small size, dense cushions, and often dark green to blackish coloration. The leaves of Grimmia are typically lanceolate or ovate and have a prominent, often toothed costa. Many species exhibit a nerve that extends beyond the leaf apex as a hair-like awn, which can be a key identification feature.

The reproductive structures of Grimmia are sporophytes, which consist of a capsule, seta, and calyptra. The capsules are typically ovoid and often have a distinctive ribbed or furrowed surface when dry. The peristome, a fringe of teeth around the mouth of the capsule, is usually present and plays a role in spore dispersal. Grimmia mosses are found worldwide, with a notable diversity in temperate and alpine regions. They are well-adapted to survive desiccation, often reviving quickly after prolonged dry periods. Their ability to colonize harsh, nutrient-poor environments makes them important pioneers in ecological succession on rock surfaces.