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| The moss families (Bryophyta, Musci) of Britain and Ireland |
Silk-mosses.
~Hypnaceae; sensu stricto, excluding Herzogiella, Isopterygiopsis, Isopterygium, Myurella, Orthothecium, Platydicta, Pseudotaxiphyllum, and Taxiphyllum
Gametophyte. Pleurocarpous; forming patches. Shoots nearly always more or less complanate (and/or secund, but sometimes not consistently so, and no more than sub-complanate in P. cavifolium). Paraphyllia absent. Pseudoparaphyllia absent (if the family is confined to Plagiothecium, with Taxiphyllum excluded). Stems with a differentiated central strand (this small but distinct). The leaves of main stems and branches usually similar in form; bilaterally symmetrical to markedly asymmetrical; ovate to lanceolate; spiral; secund, or not secund. Leaf bases decurrent (if the family is confined to Plagiothecium). The leaves double-nerved, or nerveless (rarely). The leaf nerves when present, not extending beyond the middle of the leaf, or extending beyond the middle of the leaf, but not to the tip. Leaf blade apices pointed; apically acute, or acuminate. Leaf blade margins flat, or revolute or recurved; entire to dentate. Leaf blades bordered, or not conspicuously bordered. The basal leaf cells longitudinally much elongated; rhomboidal, or linear to vermicular; smooth. The walls of basal leaf cells thin to thick; straight. The angular cells clearly differentiated (commonly enlarged), or not well differentiated. The mid-leaf cells longitudinally much elongated; narrowly rhomboidal, or linear to vermicular; smooth. The walls of the mid-leaf cells thin to thick; straight.
Plants monoecious, or dioecious; when monoecious, autoecious.
Sporophyte. Capsules exserted; erect to inclined, or horizontal; symmetrical to asymmetrical; straight to curved; sub-cylindric to ellipsoid, or pyriform; with an externally conspicuous apophysis to without an externally conspicuous apophysis. The apophysis becoming conspicuously rugose and/or twisted, or remaining smooth. Capsules smooth, or striate and becoming regularly furrowed when dry and empty; with an annulus (2–3 seriate, sometimes deciduous). Calyptra symmetrical; splitting down one side. Capsules with a peristome. The peristome double. The peristome teeth 16 (cross-striate below); 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; with a basal membranous ring, or without a basal membranous ring; with elongated “processes”. The processes of the inner peristome 16 (these keeled and perforated); alternating with the teeth of the outer peristome. The inner peristome ciliate, or without cilia. The operculum conical to rostrate. Setae long; straight; usually reddish; smooth.
Ecology. In diverse habitats, from low altitude swamps and marshes to rock ledges at high altitudes.
Cytology. Haploid chromosome number, n = 7, 8, 10, 11, 12, 20, and 25 (sometimes with one or two supernumeraries).
Representation in Britain and Ireland. 10 species (on the sensu stricto interpretation). Plagiothecium. 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 Bryideae; Order Hypnales.
Comments. This following Ochyra and O’Shea (2004) in retaining Plagiothecium as a monotypic family, and returning other genera formerly included to Hypnaceae.
Illustrations. • Plagiothecium: piliferum, with Hypnaceae Dixon. PLAGIOTHECIACEAE sensu stricto. M, Plagiothecium piliferum (Hartm.) Br. Eur. HYPNACEAE (taxa formerly referred to Plagiotheciaceae sensu lato). J, Taxiphyllum wissgrillii (Garov.) Wijk & Marg.; K, Pseudotaxiphyllum elegans (Brid.) Z. Iwats.; L, Isopterygiopsis muellerana (Limpr.) Z. Iwats.; ; N, Isopterygiopsis pulchella (Hedw.) Z. Iwats.; O, Herzogiella seligeri (Brid.) Iwats.
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. • Plagiothecium (4 species), with Herzogiella striatella: Dixon. PLAGIOTHECIACEAE: B, Plagiothecium denticulatum (Hedw.) Br. Eur.; C, Plagiothecium nemorale (Mitt.) Jaeg.; D, Plagiothecium latebricola Br. Eur.; E, Plagiothecium undulatum (Hedw.) Br. Eur. HYPNACEAE: A, Herzogiella striatella (Brid.) Iwats.
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. • Plagiothecium, with Brachytheciaceae and Hypnaceae: Berkeley. PLAGIOTHECIACEAE: 2, Plagiothecium denticulatum (Hedw.) Br. Eur., habit; a, leaf; b, capsule. 4, Plagiothecium undulatum (Hedw.) Br. Eur., habit; a, leaf; b, capsule. BRACHYTHECIACEAE: 6, Homalothecium sericeum (Hedw.) Br. Eur., habit; a, leaves; b, capsule. HYPNACEAE:1, Isopterygiopsis pulchella (Hedw.) Z. Iwats., habit; a, leaves; b, capsule. 3, Pseudotaxiphyllum elegans (Brid.) Z. Iwats., habit; a, leaf; b, capsule after lid shed. 5, Pylaisia polyantha (Hedw.) Br. Eur., habit; a, leaf; b, capsule; c, part of peristome.
From Berkeley (1863, Plate 12). 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’.
