The Moss Families of the British Isles


L. Watson and M. J. Dallwitz



Gametophyte. Plants “normal”, with leaves containing chlorophyll. Pleurocarpous (F. adianthoides, F. taxifolius), or acrocarpous, or cladocarpous; forming tufts, or forming patches, or the plants scattered. Shoots complanate. Stems with a differentiated central strand. The leaves clasping the stem, each leaf comprising a boat-shaped, clasping basal part, beyond which extends an abaxial, equitant wing with the nerve prolonged out into it; distichous. Leaf bases sheathing; decurrent. The leaves single-nerved. The leaf nerves extending beyond the middle of the leaf, but not to the tip (Octodiceras), or extending to the leaf tip; not excurrent (but sometimes percurrent). The mid-leaf cells more or less isodiametric, or more or less isodiametric to somewhat longitudinally elongated; more or less sub- hexagonal, or rounded; papillose (or mamillate). The walls of the mid-leaf cells thin, or thick; straight.

Plants monoecious, or dioecious; when monoecious, autoecious, or paroecious, or synoecious.

Sporophyte. Capsules exserted; erect, or inclined to horizontal; somewhat asymmetrical (occasionally), or symmetrical; straight, or straight to curved; more or less globose, or ellipsoid, or ovoid, or pyriform, or gibbous; with an externally conspicuous apophysis to without an externally conspicuous apophysis; smooth. Calyptra symmetrical; entire at the base, splitting down one side, or with two or more splits. Capsules with a peristome. The peristome single. The peristome teeth 16; not grouped, or in pairs; deeply cleft (bifid to about half-way); not perforated; thin, membranous, and transversely barred; interiorly exhibiting a fine longitudinal dividing line between the transverse bars. The operculum rostrate, or subulate. Setae terminal or lateral, long or short; more or less straight, or curved.

Ecology. Aquatic to mesophytic. Often but not always growing in wet situations, sometimes submerged.

Cytology. Haploid chromosome number, n = 5, 10, 11, 12, 13, 16, and 24 (occasionally with supernumeraries).

British representation. 22 species. Fissidens, Octodiceras. Northern Scotland, southern Scotland, northern England, English Midlands, East Anglia, Wales, southeast England, central southern England, southwest England, Isle of Wight, and Ireland.

Classification. Class Bryopsida; Subclass Dicranideae; Order Dicranales.

Illustrations. • 9 Fissidens species: Dixon. • 6 Fissidens species, and Octodiceras fontanum. • Fissidens adianthoides and F. taxifolius: Berkeley.

To view the illustrations with detailed captions, go to the interactive key. This also offers full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, and distributions of character states within any set of taxa.

Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 2005 onwards. The moss families of the British Isles. Version: 21st June 2009.’.