Flora of New Zealand Series

Parmelia mellissii Dodge, Ann. Mo. bot. Gdn 46: 134 (1959).

Thallus orbicular to spreading, loosely attached, 6-15 cm diam., corticolous, rarely saxicolous. Lobes rounded, 5-12 mm wide, margins crenate to dissected-isidiate, ciliate, cilia numerous, black, 1-3 mm long. Upper surface smooth, pale grey to whitish, matt, slightly reticulate-cracked, isidiate, especially at or near margins, or sorediate-isidiate, isidia soon becoming granular and sorediate. Isidia at first small, simple, terete, delicate, brown-tipped, becoming granular-sorediate and ciliate, cilia black, to 3 mm tall. Soralia marginal, derived from isidia, capitate or glomerulate, eventually becoming recurved. Lower surface black, with a naked, tan or whitish, marginal zone. Rhizines central, black, simple. Apothecia not seen. Chemistry: Cortex K+ yellow; medulla K-, C-, KC+ red, Pd-. Alectoronic and α-collatolic acids (UV ± bluish-white) and atranorin.

N: Three Kings Is and some coastal habitats in North Auckland. Still rather poorly collected in New Zealand.

Pantropical

P. mellissii is distinguished from P. crinitum by differences in chemistry, isidia which become sorediate, and longer cilia associated with the isidia, which themselves differ in the two species. P. mellissii could also be confused with Parmelina horrescens and Cetrelia braunsiana but there are characters which allow all three species to be distinguished from each other. In C. braunsiana although the chemistry is the same as in P. mellissii the isidia are smaller and more delicate and are not associated with cilia, and the colour of the lower surface is different. Parmelina horrescens has a different chemistry (it is UV-), lacks soredia and has crowded, lobular isidia which give the plant a brownish colour (P. mellissii is never brown but always whitish or greyish-white) and in general Parmelina horrescens is a much smaller plant than P. mellissii.