Platismatia tuckermanii (Oaks) WL. Culb. & CF. Culb.

       Foliose thallus very loosely attached to its substrate, formed of concave and rounded lobes with a finely cut, lace-like, crisp margin, grouped in a small tuft. Upper surface strongly reticulated in a network, pale greenish ash gray, brown-black at the margin by punctiform pseudocyphellae; lower surface whitish with large pale brownish spots with, towards the center, rare blackish rhizines. Apothecia infrequent, sessile, disc sometimes perforated, brown, prominent margin more or less crenate by pseudocyphellae. Ascospores simple, hyaline, subglobose. Photobiont: chlorococcoid. Subarctic and boreal species endemic to eastern northern North America, occurring mainly on the lower branches of trees in boreal forests (especially conifers).

N.B. This species belongs to the Platismatia glauca and Platismatia wheeleri group, which is why it is shown here for comparison.

N.B. Platismatia norvegica is quite similar, but its lobes are not as sharply cut and its coloration is paler.