Hygroamblystegium varium (Hedw.) Mönk.
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Authority
Buck, William R. 1998. Pleurocarpous mosses of the West Indies. Mem. New York Bot. Gard. 82: 1-400.
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Family
Amblystegiaceae
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Scientific Name
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Description
Species Description - Plants medium-sized, in usually dull, ± stiff, bright-, yellow-, or dark-green, often extensive, loose or dense mats. Stems creeping, to ca. 5 cm long, usually much branched, the branches erect or ascending, often crowded; in cross-section with 3-5 rows of small thick-walled cells, the outer row sometimes with thinner walls on the external surface, surrounding larger thin-walled cells, central strand small but well developed, of small thin-walled cells; paraphyllia absent; pseudoparaphyllia foliose, small; axillary hairs with a single short brown basal cell and a single elongate hyaline distal cell. Stem and branch leaves differentiated, erect- to wide-spreading dry or moist, symmetric, stem leaves narrowly oblong-ovate, to 1.4 mm long, gradually long-acuminate; costa subpercur-rent; otherwise like branch leaves. Branch leaves lanceolate to ovate-lanceolate, sometimes broadly ovate, 0.35-0.8 mm long, gradually and slenderly long-acuminate, sometimes concave; margins entire to subserrulate above, entire below, plane; costa single, relatively narrow for the genus, subpercurrent to percurrent, often flexuose above; cells mostly hexagonal, 2-3:1, smooth, firm-walled, becoming longer in the slender acumen, becoming slightly longer and ± rectangular juxtacostally and toward the insertion; alar cells poorly differentiated, relatively few, subquadrate, extending up the margin by ca. 8 cells. Asexual propagula none. Autoicous. Perichaetia enlarged, conspicuous; leaves erect, narrowly oblong-ovate, ca. 1.5-2 mm long, abruptly short-acuminate; margins entire to serrulate above, entire below, plane; costa single, broad, percurrent to short-excurrent; cells long-rectangular to linear, smooth, becoming shorter and broader toward the insertion. Setae elongate, smooth, stout, reddish, 1-2.5(-4) cm long; capsules erect to horizontal, arcuate, asymmetric, cylindric, 1.2-2.8 (-5) mm long, ± constricted below the mouth when dry; exothecial cells short-rectangular, firm-walled, not collenchymatous, slightly wavy-walled, stomata long-pored; annulus of 2-3 rows of thin-walled, deciduous cells; operculum obliquely short-rostrate; exostome teeth yellow-brown, shouldered, bordered, on the front surface cross-striolate below, coarsely papillose above, trabeculate at back; endostome with a high basal membrane, segments keeled, perforate, rarely gaping, ca. as long as the teeth, cilia in groups of 1-3, nodulose or weakly appendiculate. Spores spherical, finely papillose, 9-16(-21) µm diam. Calyptrae cucullate, naked, smooth.
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Discussion
1. Hygroamblystegium varium (Hedw.) Monk., Hedwigia 50: 275. 1911; Leskea varia Hedw., Sp. Musc. Frond. 216. 1801; Hypnum varium (Hedw.) P. Beauv., Prodr. Aethéogam. 72. 1805; Hypnum serpens var. varium (Hedw.) Müll. Hal., Syn. Musc. Frond. 2: 412. 1851; Stereodon varius (Hedw.) Mitt., J. Linn. Soc., Bot. 8: 43. 1864; Amblystegium varium (Hedw.) Lindb., Musci Scand. 32. 1879. Plate 81, figures 1-8 Discussion. As the name indicates, the plants of Hygroamblystegium varium are extraordinarily variable. The smaller plants and slender, flexuose costa, as well as the more mesic habitat requirements, distinguish it from H. fluviatile. The longer costa and shorter median cells serve to separate it from Amblystegium serpens. It also is a more robust species with a somewhat broader costa than A. serpens. Hygroamblystegium varium is usually placed in Amblystegium in North American treatments (e.g., Crum, 1983), often not on morphological groun s but because of its mesic rather than hydric habitat preference. The species has most recently been included in Hygroamblystegium by Kanda (1975) He placed the species in the genus because of the shouldered stem leaves (a character I am unable to substantiate), the somewhat stronger costa, and shorter, rhomboidal median leaf cells. My primary motivation in including the species in Hygroamblystegium is that, by doing so, both Hygroamblystegium and Amblystegium are better defined and present fewer problems in identification. The main confusion with H. varium in more temperate latitudes is not with A. serpens (the type species of that genus) but, rather, with H. tenax (Hedw.) C. Jensen. This, to me, is a stronger indication of its relationships than purely habitat preferences. If H. varium were aquatic, there would be little confusion as to its generic alliance.
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Distribution
Range. Southern Canada, United States, Mexico, Panama, Europe, northern Africa, northern Asia; Bermuda, Hispaniola (Haiti and Dominican Republic); mostly growing on bases of trees, logs, soil, humus, and rocks, in rather mesic, open habitats, from near sea level to ca. 1000 m.
Canada North America| United States of America North America| Mexico North America| Panama Central America| Europe| Algeria Africa| Egypt Africa| Tunisia Africa| Libya Africa| Morocco Africa| Sudan Africa| Russia Asia| Bermuda South America| Dominican Republic South America| Haiti South America|