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| The moss families (Bryophyta, Musci) of Britain and Ireland |
Haircap- and Smoothcap-mosses.
Gametophyte. Plants “normal”, with leaves containing chlorophyll. Acrocarpous; forming tufts, or mat or turf forming, or forming patches, or the plants scattered. Primary stems the aerial shoots arising from a rhizome-like underground stem. Mature plants 3–100 mm high. Stems with a differentiated central strand. The leaves lanceolate to narrowly lanceolate (in Polytrichum), or ovate, or lingulate; spiral; crisped when dry, or not crisped when dry. Leaf bases sheathing (mostly), or not sheathing (though broad, in Atrichum). The leaves heavily single-nerved (the distal part of the lamina consisting in Polytrichum and Pogonatum, but not in Atrichum, mainly of adaxially expanded nerve). The leaf nerves extending beyond the middle of the leaf, but not to the tip, or extending to the leaf tip; excurrent to not excurrent. Leaf blades adaxially longitudinally lamellate (with two to many chloroplast-containing lamellae along the nerves). Leaf blade apices pointed; apically acute, or acuminate. Leaf blade margins unistratose to several-stratose. Leaf blades bordered, or not conspicuously bordered.
Plants dioecious.
Sporophyte. Capsules exserted; erect to horizontal; symmetrical, or asymmetrical; straight, or curved (Atrichum); when not cuboid or trapezoid, etc., sub-cylindric to ovoid, or pyriform; obscurely to sharply angular (in Polytrichum, being then four to six angled, and rectangular or trapezoid to hexagonal in section), or neither flattened nor angular; with an externally conspicuous apophysis (usually, in Polytrichum), or without an externally conspicuous apophysis. Calyptra large and covering the well-developed capsule; usually densely or sparsely hairy, or glabrous (in Atrichum). 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. Tetraphidaceae). The peristome single (of short teeth, derived from several concentric layers of cells, and not resolvable into one or two rings). The peristome teeth in European species, 32, or 64 (64 in Polytrichum, 32 in the other genera, the teeth usually joined at their tips by an epiphragm representing the expanded apex of the columella); joined basally to form a membranous ring, or not basally joined; not deeply cleft; 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 rostellate to subulate. Setae long; straight, or flexuose.
Ecology. Occurring in mainly acid conditions. In diverse habitats.
Cytology. Haploid chromosome number, n = 7 and 14, or 21 (sometimes, in Atrichum undulatum only).
Representation in Britain and Ireland. 17 species. Atrichum (Smoothcaps), Oligotrichum (Hercynian Haircap), Pogonatum (Haircaps), Polytrichastrum (Haircaps), Polytrichum (Haircaps). 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 Polytrichales.
Illustrations. • Pogonatum and Polytrichastrum alpinum: Dixon. POLYTRICHACEAE: D, Pogonatum nanum (Hedw.) P. Beauv.; E, Pogonatum aloides (Hedw.) P. Beauv.; F, Pogonatum urnigerum (Hedw.) P. Beauv.; G, Polytrichastrum alpinum (Hedw.) G.L. Sm.
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. • 6 Polytrichum and Polytrichastrum. POLYTRICHACEAE: A, Polytrichum piliferum Hedw.; B, Polytrichum juniperinum Hedw.; C, Polytrichum strictum Brid.; D, Polytrichastrum longisetum (Sw.) G.L. Sm. ex Brid.; E, Polytrichastrum formosum (Hedw.) G.L. Sm.
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. • Atrichum angustatum, A. crispum, A. tenellum and A. undulatum: Dixon. POLYTRICHACEAE: A, Atrichum undulatum (Hedw.) P. Beauv.; B, Atrichum tenellum (Röhl.) Br. Eur.; C, Atrichum crispum (James) Sull. & Lesq.; D, Atrichum angustatum (Brid.) Brid.
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. • Oligotrichum hercynicum: Dixon. POLYTRICHACEAE: Oligotrichum hercynicum (Hedw.) Lam. & Cand.
From Dixon and Jameson (1924), the unscaled screen display approximately doubling the magnifications given with their individual figures. 1, leaf : 1a, leaf apex; 1c, cells at one third from the leaf apex. Oligotrichum hercynicum. • Atrichum, Pogonatum: Berkeley. POLYTRICHACEAE: 1, Pogonatum nanum (Hedw.) P. Beauv.; a, habit; b, leaves; c, section of a leaf; d, tranverse section of a lamella; e, young calyptra; f, capsule. 2, Pogonatum aloides (Hedw.) P. Beauv.; a, habit; b, leaves; c, young calyptra; d, capsule. 3, Oligotrichum hercynicum (Hedw.) Lam. & Cand.; a, habit; b, leaf; c, capsule. 4, Atrichum undulatum (Hedw.) P. Beauv.; a, habit; b, leaf; c, capsule; d, capsule after shedding of lid.
From Berkeley (1863, Plate 19). The approximate 1 cm scale applies to the whole plant (habit) illustrations only. • Polytrichum alpinum and P. juniperinum: Berkeley. POLYTRICHACEAE: 6, Polytrichastrum alpinum (Hedw.) G.L. Sm. var. septentrionale Swartz; a, habit; b, leaf; c, capsule. 7, Polytrichum juniperinum Hedw.; a, habit; b, leaf; c, capsule; d, the peristome; e, detail of part of the peristome.
From Berkeley (1863, Plate 18). The approximate 1 cm scale applies to the whole plant (habit) illustrations only.
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’.
