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Leptogium byssinum (Hoffm.) Zwackh ex Nyl.
Family: Collemataceae
[Collema amphineum (Nyl.) Ach.,  more]
Leptogium byssinum image
Thompson, J., 1997. American Arctic Lichens: The Microlichens.
Thallus forming a broken areolate crust to 2.5 cm broad, areolae to 3 mm broad, ashy brown to black, surface smooth to commonly granulose; paraplectenchymatous throughout, algal cells distributed through the thallus. Apothecia common, immersed or adnate, to 1 mm broad; disk concave to flat, light brown to red-brown or black; thalloid exciple entire to granulose, concolorous with the thallus, sometimes disappearing; proper exciple euparaplectenchymatous, 10 μ thick in center, to 45 μ at edges; subhymenium brownish; hymenium 95-150 μ, hyaline, with thin brown epithecium; paraphyses unbranched, 1 μ thick, little thickened at apices; asci cylindrico-clavate, 60-95 x 12-18 μ; spores 8, biseriate, ellipsoid to fusiform, apices rounded or pointed, 3-7 septate transversely, 0-1 septate longitudinally, 18-33x7-14 μ.

This species grows on soil, usually high in clay. It is a temperate circumpolar species, rarely collected perhaps because so inconspicuous, in North America ranging from New England to North Dakota and in the mountains in Colorado. It has been reported in Siberia under the name Leptogium amphi-neum Nyl. by Vainio and is included here under the possibility that it may be sought in the American Arctic.