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Masonhalea richardsonii (Hook.) Karnefelt
Family: Parmeliaceae
[Cetraria richardsonii Hook.,  more]
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Stephen Sharnoff  
Thompson, J., 1984. American Arctic Lichens: The Macrolichens.
Thallus foliose, dichotomous to irregularly divided, when dry rolled up into ball-like masses, homy in texture; the lobes sharp pointed and antler-like; upper side chestnut-brown when dry, becoming olive-green to greenish brown when moist; underside paler brown with conspicuous pruinose patches, lacking rhizinae. Outer cortex prosoplectenchymatous, 37-65 μ thick, the outer 15 μ brown pigmented, within this an inner cortex of longitudinally oriented but interwoven hyphae, about 100-125 μ in thickness, the hyphae slender, 2-2.5 μ, but quite densely arranged. Within this is a continuous layer of the algae and a loose medulla. The lower cortex is prosoplectenchymatous but lacks the inner fibrous layer of the upper cortex and is discontinuous, being lacking over the pruinose areas which appear to function as supersized pseudocyphellae for gas exchanges. The dual upper cortex reminds one of that of some of the Ramalinas but is not on both surfaces as in that genus. Apothecia rare, at the tips of lobes, the margin crenate, concolorous with the thallus, inflexed; disk 4-8 mm, brown, almost the same color as the thallus, shining; epithecium brownish, lower part brown; hypothecium pale brownish; hymenium 125 μ paraphyses capitate, the tips 6 μ; spores 8, hyaline, thin-walled, simple, ellipsoid, 7.5-12.5x5-6 μ.

Reactions: medulla K— , C+ , KC+ orange red to red, P— . UV+ .

Contents: alectoronic acid.

This species is a “wanderflechten,” growing unattached and being blown across the tundras by the winds, gathering in low spots and wet places where it spreads out in the moisture. It is a Beringian element in the flora, ranging in Siberia and in North America east to Chesterfield Inlet on the west side ol Hudson Bay and south in the mountains to British Columbia.

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Lucy Taylor  
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Stephen Sharnoff  
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