Grimmiales

Grimmiales is a small order of mosses belonging to the subclass Dicranidae. It is characterized by its typically acrocarpous growth habit, meaning sporophytes are borne at the apex of the main stem or a short branch. The leaves of Grimmiales are often stiff and erect, with a prominent midrib and a leaf tip that can be toothed or awn-like. Many species exhibit specialized leaf border cells, which can be thicker-walled and serve a protective or water-retaining function.

The sporophyte in Grimmiales is usually relatively short-lived. The capsule is typically erect and oblong, dehiscing by a conical operculum. The peristome, if present, is often composed of four broad teeth.

The order Grimmiales contains a limited number of genera and species, with Grimmia being the most well-known and diverse. Other genera include Grizzelinia and Scouleria. These mosses are found in a variety of habitats, often in exposed and dry locations such as rock surfaces, boulders, and sandy soils. They are particularly common in arid and alpine regions. Their ability to withstand desiccation is a key adaptation to these challenging environments.

Classification within Grimmiales has undergone revisions due to molecular phylogenetic studies. While traditionally placed in its own order, some studies suggest its placement within a broader context of other moss groups. Nonetheless, Grimmiales remains a distinct and recognizable assemblage of mosses with shared morphological and ecological traits.