Parmotrema reticulatum (Taylor) M.Choisy
Parmelia reticulata Taylor, Fl. hibern. 2: 148 (1836).
Thallus orbicular to spreading, loosely attached, to 12 cm diam., corticolous or saxicolous. Lobes rounded to sublinear, dissected, to 8 mm wide, crowded, margins sorediate, often revolute, ciliate. Upper surface dull, greenish-blue to pale greenish-grey, maculate at lobe tips (×10 lens), with patterned cracking continuing throughout thallus, sorediate. Soralia mainly marginal, causing lobe tips to become recurved and often capitate-hooded. Medulla white, often rusty-red when wet (decomposition products of salazinic acid). Lower surface dark brown to black, with a variable, shining naked marginal zone. Rhizines central, simple or squarrosely branched, black. Apothecia rare, pedicellate, to 8 mm wide, disc deeply concave when young, becoming ± plane with age, red-brown, perforate, thalline exciple sorediate, inflexed. Ascospores 13-16 × 9-11 µm. Pycnidia minute, black, punctiform, marginal. Chemistry: Cortex K+ yellow; medulla K+ yellow → red, C-, KC+ red, Pd+ orange. Salazinic acid and atranorin.
N: North Auckland (including Three Kings Is to Wellington). S: Nelson to Southland. St: A: C: Very widely distributed on rock and wood in both coastal and inland habitats. A common and early coloniser of fenceposts, exotic trees (especially fruit trees) in parks and gardens, more often found in disturbed habitats than on native vegetation.
Cosmopolitan
P. reticulatum is very variable but is distinguished from other closely related species by the presence of soredia, marginal cilia, reticulate-cracked upper surface and salazinic acid in the medulla (K+ yellow → red). Its non-sorediate counterpart, P. cetratum lacks both soredia and constant deep reticulate-cracking.
