The Moss Families of the British Isles


L. Watson and M. J. Dallwitz



Gametophyte. Cladocarpous; cushion-forming, or forming tufts, or mat or turf forming (often forming variously coloured tussocks and lawns). The branches in fascicles. Stems 0.3–1.2 mm in diameter; with a differentiated central strand. The leaves of main stems and branches markedly different in form. The leaves sphagnoid (the stem leaves single layered, relatively simple, usually flatter and tongue-shaped, composed entirely of hyaline cells with relatively small pores; the branch leaves also single layered, usually pointed, comprising a network of very narrow, green assimilatory cells which are interspersed among larger, empty, hyaline cells. The latter, the walls of which exhibit spiral thickenings and large, rounded pores, endow the living and dead tissues with their remarkable capacity for absorbing and retaining water). The leaves lingulate to obovate (and flat, branch leaves), or ovate to lanceolate (and concave, stem leaves); nerveless. Leaf blade apices obtuse (the branch leaves, sometimes), or pointed. The angular cells not well differentiated.

Plants monoecious (Section Cymbifolia), or dioecious (e.g., Section Truncata); when monoecious, autoecious (the archegonia developing in groups or 1–5 at the apices of short, specialised branches, while the peculiar, globose antheridia are axillary on more or less unspecialised branches).

Sporophyte. Capsules exserted (the mature capsule becoming exserted via a “pseudopodium”, which develops by elongation of the basal part of the sporogonium); erect; symmetrical; with an externally conspicuous apophysis; dehiscing via a lid; dehiscing explosively; without a peristome. The operculum convex. Setae absent.

Ecology. Aquatic to in wet places; occurring in acid conditions (rarely if ever at a pH exceeding 6.0). In marshes, pools, wet woodland, moors and damp grassland; and conspicuously forming raised and blanket bogs, with the remains persisting beneath the growing plants as the main component of peat.

Cytology. Haploid chromosome number, n = 17, 19, 38, and 42 (where sampled, often with 2 or 4 supernumeraries).

British representation. About 35 species. Sphagnum. 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 Sphagnopsida; Order Sphagnales.

Illustrations. • 6 Sphagnum species: Dixon. • 5 Sphagnum species. • 7 Sphagnum species. • Sphagnum, with Andreaea: 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.’.