General:
Common Name: The Tarpaper Lichens. Stresses the blackish nonstratified medulla that becomes somewhat swollen, translucent and jellylike when moistened.
Minute to occasionally large nonstratified foliose lichens (gelatinous when wet), lacking true cortex, (except cortex present on apothecial margin: see below) isidiate or not, lobes closely appressed to semi-erect, 0.5–10 (–15) mm wide, thin to thick. Upper surface dark olive brownish or blackish (ours), dull. Lower surface dark, rhizines absent or rarely present. Medulla absent. Photobiont blue-green.
Apothecia located over upper surface or marginal, with thalline margin, disc reddish brown; spores 2- to multicelled, ellipsoid to needle-shaped/acicular, (4–) 8 per ascus. Over bark, earth and rock, usually base-rich.
Notes: Collema is a taxonomically difficult genus comprising about 80 species, of which 35 are known to occur in North America and 20 in B.C. Chemistry is of no diagnostic value in this genus. Two keys are provided. The first key emphasizes macroscopic vegetative characters, though spore characters have been incorporated in some places. The second key, to nonisidiate species, stresses spore characters and is more technical.

Source:  Lichens of British Columbia

If more than one illustration is available for a species (e.g., separate illustrations were provided for two subspecies) then links to the separate images will be provided below. Note that individual subspecies or varietal illustrations are not always available.

Illustration By:  Trevor Goward

Synonyms and Alternate Names:
Collema arcticum Lynge