E-Flora BC: Electronic Atlas of the Flora of British Columbia

General:
Common Name: The Rocktripe Lichens. Traditional, reflecting both the strict occurrence of the species over rock and (apparently) the use of certain species as food in times of famine.
Small to medium stratified foliose lichens, umbilicate, rotund to subrotund, corticate above and below, isidiate or more often not, thalloconidiate or not, lobes developed or not, thallus averaging to 0.5–7 (–15+) cm across, thin or occasionally thick. Upper surface greyish to dark brown. Lower surface tan, brown or black, naked or more or less covered in rhizines, plates and/or papillae. Medulla white. Photobiont green.
Apothecia located over upper surface, disc even or variously fissured or with central protruding button, black; spores simple or multi-celled, ellipsoid, colourless or occasionally brown, (1–) 8 per ascus.
Notes: Umbilicaria is primarily a boreal and arctic genus consisting of approximately 45 species worldwide. Of the 28 species known to occur in North America, 20 are reported for B.C. Earlier authors arranged the species listed below in as many as four genera — Actinogyra, Agyrophora, Omphalodiscus and Umbilicaria — though it is now customary to accommodate them in Umbilicaria. Strongly pustulate species, however, should be checked for in Lasallia. Gyrophoric acid (C+ red) is present in most Umbilicaria species, and norstictic and stictic acids also occur on occasion. Chemistry, however, is of little diagnostic value in this genus and is omitted.

Species description:
Isidia absent; lower surface naked or bearing plates or rhizines, pitted or not AND
Thallus distinctly foliose, attached to substrate by single, more or less central holdfast; upper surface occasionally perforate or segmented, but never chinky-cracked; distribution and ecology various AND
Lower surface (excluding rhizines) jet black throughout or partly covered in sharply demarcated, black, sooty patches (i.e., thalloconidia present or apparently present) AND
Lower surface (or sometimes lobe margins) bearing numerous rhizines and/or platelike outgrowths AND
Upper surface at most moderate pruinose; greyish, brownish or blackish AND
Upper surface lacking perforations or only sparsely perforate; upper surface lacking rhizines AND
Rhizines not at all ball-tipped AND
Lower surface more or less dark, but without sharply demarcated sooty patches; rhizines abundant; apothecia usually abundant; ecology and distribution various; frequent or infrequent AND
Lower surface generally brownish toward thallus periphery; “rhizines” distinctly grainy textured (graininess visible with hand lens), oriented more or less parallel to lower surface and forming interwoven network over it; apothecia generally rounded in outline

OR

Isidia absent; lower surface naked or bearing plates or rhizines, pitted or not AND
Thallus distinctly foliose, attached to substrate by single, more or less central holdfast; upper surface occasionally perforate or segmented, but never chinky-cracked; distribution and ecology various AND
Lower surface (excluding rhizines) pale or brown or, if partly grading to black, then thalloconidia absent (i.e., lacking sharply demarcated black, sooty patches); apothecia usually abundant AND
Lower surface (or sometimes lobe margins) bearing numerous rhizines and/or platelike outgrowths AND
Lower surface bearing platelike outgrowths, these often dissected, forming network of interwoven “rhizines” that may in part resemble true rhizines AND
Upper surface occasionally cracked, but not at all distinctly segmented; thallus margins not perforate when mature