Arthonia polymorpha
=Arthonia aspera C.Knight, Trans. N. Z. Inst. 15: 351 (1883) non. Leight.
=Arthonia tenuissima C.Knight, Trans. N. Z. Inst. 15: 352 (1883).
Arthonia aspera. Type: New Zealand. Sine loco, Charles Knight – WELT
Arthonia tenuissima. Type: New Zealand. Sine loco, Charles Knight – WELT.
Description : Thallus thin, grey-green to whitish, smooth to somewhat roughened, delimited by a thin, black prothalline line. Apothecia sessile, 0.3–1 mm diam., round to irregular, rarely elongate or branched, often clustered; disc black, epruinose. Ascospores ovoid-ellipsoidal, colourless to brown-black with age, 5-septate, the end cell often larger, 14–20 × 4.5–7.5 μm.
N: Wellington. Known also from North America, the Caribbean, Brazil (Fink 1935; Esslinger & Egan 1995).
Pantropical
Illustrations : Knight (1883: pl. XXXV, fig. 7 – as Arthonia aspera; pl. XXXVIII, fig. 30 – as Arthonia tenuissima).
Arthonia polymorpha is characterised by: the corticolous habit; the whitish to grey-green slightly roughened thallus; sessile, black, epruinose apothecia; 5-septate ascospores, colourless to brown-black, the end cell often larger, 14–20 × 4.5– 7.5 μm.
