The Moss Families of the British Isles


L. Watson and M. J. Dallwitz




Gametophyte. Pleurocarpous; slender mosses, forming patches (these tight, glossy and yellowish-tinged), or growing through other Bryophytes. Primary stems procumbent. Shoots (sub-) complanate, or not complanate. Paraphyllia absent. Pseudoparaphyllia absent. Stems yellowish, or green. The leaves of main stems and branches similar in form; bilaterally symmetrical (to only slightly asymmetrical); ovate, or lanceolate; spiral; (sub-) secund, or not secund. Leaf bases not decurrent. The leaves nerveless, or double-nerved, or single-nerved (sometimes, in S. demissa). The leaf nerves when present, not extending beyond the middle of the leaf ("nerve absent or short and double" according to British authors, although their own descriptions represent leaves of S. demissa as "nerveless or with faint traces of a single or double nerve"); without stereids. Leaf blade apices pointed; apically acute to acuminate. Leaf blade margins flat, or revolute or recurved (proximally); unistratose; distally denticulate, or entire. Leaf blades not conspicuously bordered. The basal leaf cells longitudinally much elongated; rhomboidal to linear, or vermicular; smooth. The walls of basal leaf cells straight. The angular cells clearly differentiated (these large, forming small auricles). The mid-leaf cells longitudinally much elongated; rhomboidal to linear, or vermicular; smooth. The walls of the mid-leaf cells straight.

Plants monoecious, or dioecious; when monoecious, autoecious.

Sporophyte. Capsules exserted; inclined to horizontal; symmetrical; straight; ellipsoid; without an externally conspicuous apophysis; smooth; without an annulus. Calyptra symmetrical; splitting down one side. Capsules with a peristome. The peristome double. The peristome teeth 16; not grouped; not deeply cleft (?); not perforated; thin, membranous, and transversely barred; exteriorly with a fine longitudinal dividing line between the transverse bars. The inner peristome well developed, or reduced; with a basal membranous ring; with elongated “processes”. The processes of the inner peristome alternating with the teeth of the outer peristome. The inner peristome ciliate. The operculum rostrate. Setae long; flexuose; smooth, or rough.

Ecology. In wet places to mesophytic. On lightly to moderately shaded rocks in humid habitats, at low altitude (S. demissum), or to 500 m (S. micans).

British representation. 3 species. Sematophyllum. Northern Scotland, southern Scotland, northern England, Wales, and Ireland.

Classification. Class Bryopsida; Subclass Bryideae; Order Hypnales.

Illustrations. • Sematophyllum demissum and S. micans: Dixon. • Sematophyllum demissum, with Campyliaceae and Hypnaceae: 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.’.