Parmelina quercina

A foliose lichen occurring on the bark of Quercus, with flat lobes; upper surface of the thallus bluish grey, lower surface dark brown with rhizines that anchor it to the substrate, with frequent disc-shaped reddish-brown apothecia.

Thallus containing abundant unicellular green algae of the genus Trebouxia; these algae are spherical, green, 10 to 18 µm in diameter.

Asci subcylindrical to clavate, club- or sack-shaped, eight-spored, 40 to 50 µm long, 11 to 14 µm wide, with biseriate (in two rows) to irregular spore arrangement within the ascus, and an amyloid apical apparatus in Melzer's reagent or IKI.

Paraphyses filiform, simple or very sparsely branched, multiseptate, 2.5 to 3 µm wide, with slight apical enlargements of 3 to 4 µm, covered with abundant reddish-brown amorphous substance at the apex, extending only very slightly above the asci.

Ascospores ellipsoidal, smooth, hyaline, moderately thick-walled, 8.5 to 11 µm long, 5 to 6.5 µm wide, containing one or two oil droplets (guttules) inside.

Herbarium material available: JTP2154/24.