Mosses come in a wide variety of forms, but all are based on a stem and leaf structure. The stem may be branched to a greater or lesser degree. Broadly, they can be divided into two groups - acrocarpous and pleurocarpous mosses.
Further growth takes place via branches off the main stem.
An example of an acrocarpous moss is Bryum pseudotriquetrum . Pleurocarpous mosses have a main stem of unlimited growth , and usually much-branched. Inflorescences are produced on short branches. An example of a pleurocarpous moss is Hyocomium armoricum . With experience it is usually a simple matter to tell these two groups of mosses apart, and this is an important early step when attempting to identify an unknown specimen.