Nardia compressa (Nardia compressa)
Description
Nardia compressa Growing in cushions or thinner mats with erect or prostrate stems and sometimes forming extensive turfs; usually dark or mid-green in shaded sites, but can be redbrown or dark red through to a lurid, dark purple in more exposed sites. Shoots are usually 1-2 mm wide (viewed from the side), and 1-2 cm long, but can be up to 15 cm in large patches in upland springs. The leaves are rounded and often wider than long (3 mm wide and up to 1.8 mm long), closely set and laterally compressed so that the upper surfaces of the leaves are pressed together, particularly in the upper leaves, and projecting beyond the stem both above and below. Underleaves are present, but are usually small and not easy to see with a hand lens. The laterally compressed shoots with the back margin of the leaf projecting well below the stem should mean that this plant is easily identified. N. scalaris (p. 152) differs in the leaf insertion, is hardly laterally compressed and has peg-like underleaves which are usually visible with a hand lens. Jungermannia exsertifolia (p. 145) grows in upland flushes and forms large dark-coloured turfs, but the orientation of the leaves is different, with the back margin hardly projecting below the leaf, the shoots are not laterally compressed, and underleaves are absent. Grows in permanently wet or frequently inundated, acidic places on rocks and stones in turbulent streams and rivers, and occasionally embedded in sand and gravel. N. compressa most typically forms spongy masses in cold, slow-flowing headwaters of upland streams. In burns and flushes associated with very latelying snow, it can form pure patches covering many square metres.
Taxonomic tree
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Domain: Eukarya
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Kingdom: Plantae
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Phylum: Hepaticophyta
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Class: Jungermanniopsida
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Order: Jungermanniales
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Family: Gymnomitriaceae
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Genus: Nardia
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