|
| The moss families (Bryophyta, Musci) of Britain and Ireland |
Four-tooth Mosses.
Gametophyte. Acrocarpous; forming tufts, or forming patches, or gregarious. Rosette plants (Tetrodontium), or non-rosette plants. Mature plants to 2–15(–35) mm high. Stems with a differentiated central strand (?), or without a differentiated central strand (Tetradontium). The leaves orbicular to ovate, or lanceolate; spiral; nerveless, or single-nerved (mostly). The leaf nerves when present, extending beyond the middle of the leaf, but not to the tip. Leaf blade apices pointed; apically acute, or acuminate. Leaf blade margins entire. The basal leaf cells more or less isodiametric to somewhat longitudinally elongated, or longitudinally much elongated; rectangular to rounded; smooth. The walls of basal leaf cells thick; straight. The angular cells not well differentiated. The mid-leaf cells more or less isodiametric to somewhat longitudinally elongated; rectangular to rounded, or linear; smooth. The walls of the mid-leaf cells thick; straight.
Plants monoecious; autoecious (usually), or synoecious. Plants gemmiferous (in T. pellucida only); the gemmae of T. pellucida in leaf axils and or on rhizoids.
Sporophyte. Capsules exserted; erect; symmetrical; elongate; straight; sub-cylindric to ovoid; without an externally conspicuous apophysis; smooth; without an annulus. Calyptra symmetrical; plicate (Tetraphis), or not plicate; with two or more splits. Capsules with a peristome (the teeth retaining a cellular structure, and in this respect contrasting with conventional moss peristomes, where these comprise only the thickened parts of cell walls remaining after the rest of the cells have degenerated; cf. only the Polytrichaceae). The peristome ostensibly single. The peristome teeth 4; not basally joined; not deeply cleft; not perforated; solid, without transverse bars (derived from several concentric series of sporogonium cells). The processes of the inner peristome opposite the teeth of the outer peristome. The operculum conical. Setae 4–15 mm long; straight.
Ecology. Occurring in acid conditions, or neutral pH conditions and acid conditions. Tetraphis on rotting wood, peat and sandstone rocks, Tetradontium associated with acidic rocks in heavy shade by streams and rivers.
Cytology. Haploid chromosome number, n = 6, 7, and 8.
Representation in Britain and Ireland. 3 species. Tetraphis, Tetrodontium. 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 Polytrichopsida; Order Tetraphidales.
Illustrations. • Tetraphis pellucida and Tetrodontium brownianum: Dixon. TETRAPHIDACEAE: F, Tetraphis pellucida Hedw. G, Tetrodontium brownianum (Dicks.) Schwaegr.
From Dixon and Jameson (1924), the unscaled screen display approximately doubling the magnifications given with their individual figures. 1, leaf or stem leaf where these differ; 2, branch-leaf; 3, perichaetial leaf; 4, perigonial leaf; 5, capsule; 6, peristome; 7, calyptra; 8, spores; 9, inflorescence; 10, gemmae; 11, paraphyllia; 12, stoma of capsule; *, plant, or part of one.
Qualifications: a, apex; b, base; c, cells at one third from the apex; cv, ventral aspect of cells; cd, dorsal aspect of cells; bc, basal cells; x, section. • Tetraphis pellucida: Berkeley. TERAPHIDACEAE: Tetraphis pellucida Hedw.; a and b, habit of capsule-bearing and gemmiferous plants, respectively; c, leaf; d, apex of gemmiferous shoot; e, young calyptra; f, capsule with lid; g, capsule after fall of lid; h, peristome.
From Berkeley (1863, Plate 19). The approximate 1 cm scale applies to the whole plant (habit) illustrations only. • Tetrodontium browneanum (Berkeley). Tetrodontium browneanum (Dicks.) Schwagr. a & b, plants; c, leaf; d, perichaetial leaves; e and f, sporangium and peristome. Berkeley (1863), Plate 19.
We advise against extracting comparative information from the descriptions. This is much more easily achieved using the DELTA data files or the interactive key, which allows access to the character list, illustrations, 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. See also Guidelines for using data taken from Web publications.
Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 2005 onwards. The moss families (Bryophyta, Musci) of Britain and Ireland. Version: 5th August 2019. delta-intkey.com’.
