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Common Name: The Paw Lichens. Alludes to the presence of brown, paw-like apothecia on the lower surface; in all other genera the apothecia are located over the upper surface or along the lobe margins.
Small to medium or large stratified foliose lichens, corticate above and below, sorediate or isidiate or not, lobes loosely appressed to loosely attached, short to elongate, averaging to 0.5–2 (–3) cm wide, thin. Upper surface greenish, greyish or brownish, dull or shiny. Lower surface pale to dark, naked or more or less covered in dense woolly tomentum, occasionally also tuberculate, lacking rhizines. Medulla white (yellow to orange). Photobiont green and/or blue-green.
Apothecia appressed over lower surface near lobe tips, disc brown; spores 4-celled, spindle-shaped, pale brown, 8 per ascus.
Over trees, logs, mossy rocks.
Notes: Nephroma is a cosmopolitan genus of about 40 species worldwide. Nine are known from North America and all occur in B.C. Although thin-layer chromatography has been used successfully in the elucidation of some Nephroma species (see for example James and White 1987), spot tests are of little taxonomic value in this genus.
Photobiont a dark blue-green cyanobacterium; upper surface brownish, greyish, or if greenish, then also sorediate or isidiate; ecology and distribution various AND
Lower surface distinctly and more or less evenly covered in dense, woolly hairs, these tending to obscure the fine details of the surface wrinkles; soredia absent AND
Upper surface brownish, not at all maculate; lower surface dark brownish AND
Upper surface more or less plane; isidia absent or, if isidia-like lobules present, then these usually occurring singly AND
Lower surface lacking “warts”/papillae; backs of apothecia occasionally rough-textured, never hairy; lobe margins distinctly lobulate
Photobiont a dark blue-green cyanobacterium; upper surface brownish, greyish, or if greenish,
then also sorediate or isidiate; ecology and distribution various AND
Lower surface nakedor minutely woolly, “woolliness” not obscuring fine details of surface wrinkles; soredia present or absent AND
Thallus lobulate, but lacking soredia or isidia (Note: lobules may, however, occasionally appear isidia-like; in this case “isidia” are usually borne singly) AND
Lobe margins and/or upper surface usually lobulate; upper surface naked or minutely woolly; medulla white or orange, K- or K+ reddish; apothecia present or absent; generally over rock AND
Medulla white throughout, K-; widespread
Two varieties occur in B.C.: 1. ssp. helveticum - Marginal lobules minute, 0.1–0.4 mm in length, generally dorsiventral; mostly over rock; and 2. ssp. sipeanum (Gyelnik) Goward & Ahti - Marginal lobules varying in size, but generally 0.3–0.5 (–1.5) mm in length, often cylindrical; over bark and (occasionally) over mossy rock
All spot tests negative.
Source: Lichens of British Columbia