The Moss Families of the British Isles


L. Watson and M. J. Dallwitz


~Dicranaceae, and cf. Ditrichaceae. Excluding Amphidiaceae.

Gametophyte. Acrocarpous (usually); forming tufts (mostly), or cushion-forming, or forming patches. Mature plants when erect or ascending, 5–150 mm high. Shoots not complanate. Stems 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, or lingulate; not distichous; spiral; secund (occasionally, e.g. sometimes in Dicranoweisia crispula), or not secund; crisped when dry (very commonly), or not crisped when dry (e.g., Dichodontium). Leaf bases sheathing, or not sheathing. The leaves single-nerved. The leaf nerves extending beyond the middle of the leaf, but not to the tip, or extending to the leaf tip; excurrent (sometimes, in Oncophorus), or not excurrent; incorporating stereids. Leaf blades not lamellate. Leaf blade apices not hyaline. Leaf blade margins flat, or revolute or recurved; unistratose, or bi-stratose; entire to dentate. Leaf blades not conspicuously bordered. The basal leaf cells more or less isodiametric to longitudinally much elongated; rectangular to linear; smooth. The angular cells clearly differentiated (Dicranoweisia, Oncophorus), or not well differentiated. The mid-leaf cells more or less isodiametric to longitudinally much elongated; quadrate to rhomboidal; papillose (or mamillose, in Rhabdoweisia), or smooth.

Plants monoecious (mostly), or dioecious (in Dichodontium); when monoecious, autoecious.

Sporophyte. Capsules exserted; erect, or inclined; symmetrical, or asymmetrical; elongate; straight, or curved; sub-cylindric to ovoid, or pyriform, or gibbous; with an externally conspicuous apophysis, or without an externally conspicuous apophysis (mostly); smooth (e.g., in Dichodontium), or striate and becoming regularly furrowed when dry and empty; with an annulus, or without an annulus. Calyptra splitting down one side. Capsules dehiscing via a lid; with a peristome. The peristome when present, i.e. usually, single. The peristome teeth 16; not grouped; deeply cleft, or not deeply cleft (e.g., Rhabdoweisia); not perforated, or perforated; thin, membranous, and transversely barred (and transversely articulated); interiorly exhibiting a fine longitudinal dividing line between the transverse bars; smooth, with oblique striations that alternate with each articulation. The operculum conical to subulate. Setae usually long; curved, or straight.

Ecology. In wet places, mesophytic, and xerophytic; occurring in basic habitats (?), or neutral pH conditions, or acid conditions (with most Cynodontium spp. favouring non-basic habitats). In diverse habitats.

Cytology. Haploid chromosome number, n = 7, 12, 13, 14, and 15 (sometimes with a supernumerary).

British representation. 14 species. Cynodontium (Dog-tooth Mosses), Dichodontium (Fork- and Forklet Mosses), Dicranoweisia (Pincushions), Oncophorus (Spur-mosses), Oreoweisia (Brunton’s Dog-tooth), Rhabdoweisia (Streak-mosses). 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.

Illustrations. • Cynodontium, Oreoweisia and Rhabdoweisia (with Ditrichaceae and Seligeriaceae): Dixon. • Cynodontium, Dichodontium and Onchophorus (with Dicranella and Trematodon): Dixon. • Dichodontium and Dicranoweisiam, with Dicranaceae and Blindia: Dixon. • Oreoweisia (with assorted dicranoid taxa): Berkeley. • Rhabdoweisia crispata (with assorted other taxa): 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.’.