The Moss Families of the British Isles


L. Watson and M. J. Dallwitz


Swan-neck Mosses, Bow-mosses, Fork-mosses, etc.

Excluding Ditrichaceae, Seligeriaceae, Leucobryaceae and Rhabdoweisiaceae.

Gametophyte. Acrocarpous (usually), or pleurocarpous (e.g., Dicranum scoparium); forming tufts, or mat or turf forming, or forming patches, or growing through other Bryophytes. Mature plants when erect or ascending, 2–150 mm high. Stems tomentose below (commonly, e.g. in Dicranum, and Campylopus often with red or red-brown tomentum), or not tomentose; with a differentiated central strand. The leaves neither sphagnoid nor leucobryoid. The leaves ovate, or lanceolate to narrowly lanceolate (commonly), or linear to subulate; not distichous; spiral; secund (or falcato-secund), or not secund; tightly to loosely crisped when dry, or not crisped when dry; single-nerved. The leaf nerves extending beyond the middle of the leaf, but not to the tip to extending to the leaf tip; excurrent to not excurrent (sometimes percurrent); incorporating stereids. Leaf blade apices conspicuously hyaline (3 Campylopus spp.), or not hyaline. Leaf blade margins unistratose, or bi-stratose. The basal leaf cells somewhat longitudinally elongated to longitudinally much elongated; rectangular to linear; smooth. The angular cells clearly differentiated (mostly, sometimes forming auricles), or not well differentiated (Dicranelloideae). The mid-leaf cells more or less isodiametric to longitudinally much elongated; quadrate to linear; smooth.

Plants monoecious, or dioecious (commonly); when monoecious, autoecious, or paroecious.

Sporophyte. Capsules exserted; erect, or inclined; symmetrical, or asymmetrical; straight, or curved; sub-cylindric, or ovoid, or pyriform (rarely), or gibbous; with an externally conspicuous apophysis (occasionally), or without an externally conspicuous apophysis (mostly); smooth (in Dicranum, etc.), or striate and becoming regularly furrowed when dry and empty (commonly, in some genera); with an annulus, or without an annulus; dehiscing via a lid; with a peristome. The peristome single. The peristome teeth 16 (usually), or 32 (if divided to the base); not grouped; deeply cleft (often almost to the base, into 32 divisions); not perforated, or perforated; thin, membranous, and transversely barred (and transversely articulated); usually interiorly exhibiting a fine longitudinal dividing line between the transverse bars (if not divided to the base); flat, papillose above and vertically striate-pitted below. The operculum rostellate to subulate. Setae usually long; curved, or straight.

Cytology. Haploid chromosome number, n = 7, 10, 11, 12, 13, 14, 15, 22, and 23 (sometimes with one or 2–3 supernumeraries).

British representation. About 46 species. Aongstroemia (Sprig-moss), Arctoa (Fork-moss), Campylopus (Swan-neck Mosses), Dicranodontium Bow-mosses), Dicranella (Forklet-mosses), Dicranum (Fork-mosses), Kiaeria (Fork-mosses), Paraleucobryum (Long-leaved Fork-moss). 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.

Comments. The leaves usually more or less uniform in size up the stems.

Illustrations. • Dicranella (with Rhabdoweisiaceae and Trematodon): Dixon. • Campylopus and Dicranella, with Rhabdoweisiaceae and Blindia: Dixon. • 7 Campylopus species. • Arctoa, Campylopus, Dicranum, Dicranodontium and Kiaeria. • 6 Dicranum species: Dixon. • 5 Dicranum species, 2 Dicranodontium species, and Paraleucobryum: Dixon. • Arctoa, Campylopus, Dicranum and Dicranella: 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.’.