The Moss Families of the British Isles


L. Watson and M. J. Dallwitz



Gametophyte. Pleurocarpous; forming tufts, or forming patches (dark green). Primary stems procumbent (the plants small). Mature plants 15–30 mm high. Shoots complanate, or not complanate. Pseudoparaphyllia absent. Stems without a differentiated central strand. The leaves bilaterally symmetrical, or markedly asymmetrical; lanceolate to linear (complanate or concave, often asymmetric); spiral (actually 6 ranked, though complanate, in Calyptochaeta apiculata). Leaf bases decurrent. The leaves single-nerved, or double-nerved to single-nerved (forked, in Calyptrochaeta). The leaf nerves not extending beyond the middle of the leaf to extending beyond the middle of the leaf, but not to the tip. Leaf blade apices pointed; apiculate (Calyptrochaeta), or not apiculate; apically acute to acuminate; not hyaline. Leaf blade margins flat; unistratose, or bi-stratose (Calyptrochaeta); entire (Daltonia), or denticulate to dentate (above, in Calyptrochaeta). Leaf blades bordered. The basal leaf cells somewhat longitudinally elongated; irregularly to elongate hexagonal, or rounded, or rhomboidal; smooth. The walls of basal leaf cells thin to thick; straight. The angular cells not well differentiated. The mid-leaf cells somewhat longitudinally elongated; irregularly hexagonal, or rhomboidal; smooth. The walls of the mid-leaf cells thin to thick; straight.

Plants monoecious, or dioecious (Calyptrochaeta); when monoecious, autoecious.

Sporophyte. Capsules exserted; erect; symmetrical; straight; ellipsoid, or ovoid, or pyriform (short-necked); not waisted; neither flattened nor angular; with an externally conspicuous apophysis to without an externally conspicuous apophysis; smooth; with an annulus (in Calyptrochaeta, of large cells, and falling with the lid), or without an annulus (Daltonia). Calyptra glabrous (sometimes), or hairy; symmetrical; with two or more splits. 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 to reduced; about equalling the outer; without a basal membranous ring; with elongated “processes” (these keeled). The processes of the inner peristome 16; alternating with the teeth of the outer peristome (papillose). The inner peristome without cilia. The operculum rostrate. Setae about 2 cm long, stout; straight; deep red; rough (papillose).

Ecology. In wet places, or mesophytic (in localities with high rainfall). Daltonia on humus, decaying wood or rocks by streams and on tree boles, to 500m; Calyptrochaeta on sheltered soil or sandstone boulders, near the sea.

British representation. 2 species. Calyptrochaeta (Southern Hookeria), Daltonia (Irish Daltonia). Northern Scotland, southern Scotland, and Ireland (Daltonia), or southeast England and southwest England (East Sussex and the Isles of Scilly, Calyptrochaeta).

Classification. Class Bryopsida; Subclass Bryideae; Order Hookeriales.

Comments. Rhizoids 1–3 pinnately branched.

Illustrations. • Cyclodictyon, Daltonia, and Hookeria: Dixon. Daltonia splachnoides. Cyclodictyon laetevirens. Hookeria lucens. • Daltonia, with Fontinalaceae, Hookeriaceae, etc.: 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.’.