Flavoplaca flavocitrina (Nyl.) Arup, Fröden & Sochting

= Caloplaca flavocitrina  (Nyl.) H. Olivier

   Thallus crustose, more or less continuous formed of small flat and slightly flexuous scales with a soredia margin, the soredia can sometimes cover the entire surface from the margin, thallus typically lemon-yellow, green-yellow, in the sun but green or yellow greenish in the shade and on moist substrates, soredia are bright yellow but become paler, greenish-grey and mealy in old age. Adnate apothecia at least initially, 0.3-0.8 mm in diameter, flat disc, generally a little more colored than the thallus, margin concolor to the thallus more or less persistent, smooth or very little sorediate. Polarilocular spores, 9-13 x 5-7 µm with a septum of 2.5-4 µm. Thallus and apothecia K+ purple. Common species found on basic substrates: limestone rocks, cement, mortar, concrete, etc., also, but more rarely, on the basic bark of trees.

N.B. This taxon belongs to the Flavoplaca citrina agg group. and is not separated from it by certain authors... We take here this taxon, variously interpreted, in the sense of the British authors.

N.B. This taxon can be distinguished (with difficulty!) from Flavoplaca citrina agg by its mealy soredia in old age, paler than the cortex, by its apothecia with a smooth or almost smooth margin, the greener colors of its sharp thallus with its bright yellow soredia and its occurrence on bark as well as rocks or concrete .  Flavoplaca arcis has blastidia and the thallus margin is finely lobed.