The Moss Families of the British Isles


L. Watson and M. J. Dallwitz


Long-necked Moss.


Gametophyte. Acrocarpous; forming tufts (the tufts green or brownish). Mature plants short, about 3–10 mm high. The leaves neither sphagnoid nor leucobryoid. The leaves bilaterally symmetrical; proximally ovate to lanceolate, or subulate (distally); not distichous; spiral. Leaf bases sheathing. The leaves single-nerved. The leaf nerves extending to the leaf tip; excurrent (the sheathing base rapidly narrowed to the excurrent subula, which is at its longest around the middle of the shoot, where it comprises about half the length of the lamina, and consists mainly of nerve). Leaf blade apices acuminate. Leaf blades not conspicuously bordered. The basal leaf cells somewhat longitudinally elongated to longitudinally much elongated; rectangular to linear; smooth. The walls of basal leaf cells straight. The angular cells not well differentiated. The mid-leaf cells more or less isodiametric to longitudinally much elongated; quadrate to linear; smooth. The walls of the mid-leaf cells thin to thick; straight.

Plants monoecious; autoecious.

Sporophyte. Capsules exserted; inclined; symmetrical, or asymmetrical; curved; including the neck, clavate (bright orange-red); with an externally conspicuous apophysis (the apophysis constituting a narrow neck which is asymmetric at its base and is about as long as the rest of the capsule); striate and becoming regularly furrowed when dry and empty; with an annulus, or without an annulus. Calyptra symmetrical; splitting down one side, or with two or more splits. Capsules dehiscing via a lid; with a peristome. The peristome single. The peristome teeth 16, or 32; joined basally to form a membranous ring (usually, forming a short membrane), or not basally joined; not grouped; deeply cleft to not deeply cleft (irregular, from deeply cleft into 32 divisions to almost entire); not perforated, or perforated; thin, membranous, and transversely barred; when incompletely cleft, interiorly exhibiting a fine longitudinal dividing line between the transverse bars. The operculum rostrate. Setae 1–3 cm long; straight; yellow; smooth.

Ecology. Occurring in acid conditions. Montane, on moist, peaty soil.

British representation. 1 species. Trematodon. Northern Scotland (the only ‘British’ representative of the family being T. ambiguus, last recorded from the base of Schiehallion in mid-Perthshire in 1883!).

Classification. Class Bryopsida; Subclass Dicranideae; Order Dicranales.

Illustrations. • Trematodon ambiguus: Dixon. Trematodon ambiguus. • Trematodon (with Dicranella and Rhabdoweisiaceae): Dixon.

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.’.