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General:
Common Name: The Brownette Lichens. Stresses the miniature size and superficial resemblance to certain species of “brown” lichens (e.g., Melanelia and Neofuscelia).
Minute to small stratified to nonstratified foliose or occasionally squamulose lichens, corticate above and below, isidiate or not, lobes closely appressed or partly semi-erect, elongate-linear, linear or occasionally short, averaging to (0.1–) 0.2–0.8 (–l.5) mm wide, thin. Upper surface dark olive-brown or blackish, smooth or longitudinally striate. Lower surface dark or occasionally pale, bearing blue-green or occasionally pale rhizines, these often extending outward from thallus as prothallus. Medulla white. Photobiont blue-green.
Apothecia located over upper surface, disc dark brown to black; spores 2- to 4-celled, ellipsoid to somewhat spindle-shaped/fusiform, colourless, (4-) 8 per ascus.
Over rock, rarely over bark.
Notes: Placynthium is primarily a temperate genus, consisting of approximately 25 species worldwide. Of the six species occurring in North America, five are reported from B.C. In this taxonomically rather difficult genus, conclusive identification of some species requires detailed anatomical studies (see Henssen 1963d). No lichen substances have been reported.
Species description:
Thallus broadly or narrowly attached to substrate, but not umbilicateAND
Thallus brownish; lobes not at all swollen; substrate variousAND
Lobes either mostly appressed to substate or, if erect, then over rock AND
Lower surface pale AND
Inland or, if occurring west of coast ranges, then restricted to upland localities AND
Peripheral lobes strongly convex, averaging to less than 0.2 mm wide; over limestone
Comments:
The B.C. material can be assigned to var. isidiatum Henssen. The type locality of this variety is near Crown Lake in Marble Canyon, near Lillooet, B.C.
Source: Lichens of British Columbia |
