Flora of New Zealand Series

C. citrina (Hoffm.) Th. Fr., Nova Acta R. Soc. Scient. upsal. ser. 3, 3: 218 (1861).

Verrucaria citrina Hoffm., Dtsch. Fl.: 198 (1796).

Thallus crustose, effuse, coarsely granular-sorediate in a ± diffract-areolate crust, or ± thinly scattered, yellow to pale lemon yellow or green-yellow, K+ purple, saxicolous. Apothecia rather rare, 0.2-0.6 mm diam., disc plane, matt, orange, thalline margin granular, concolorous with thallus, occluded with age. Ascospores biseriate, ellipsoid with rounded ends, straight, 10-15 × 4.5-8 µm, septum c. ⅓ length of spore. Chemistry: Emodin, parietin, xanthorin, fallacinal.

S: Canterbury, Weka Pass. On limestone rocks, among colonies of C. saxicola and C. decipiens. Probably more widespread on limestone in New Zealand.

Cosmopolitan

Easily recognised by the scattered, yellow or green-yellow granular thallus.