Parmeliella aggregata
Holotype: New Zealand. Otago, Rigney, 8 km S of Millers Flat, on willow bark, 30.iii.1998, D.J. Galloway 1424 – OTA. Isotype – BG.
Description : Thallus squamulose, forming rosettes or irregularly spreading 1–4(–5) cm diam., corticolous, spreading on a white to blue-black, arachnoid prothallus, visible at margins or between lobes. Lobes radiating, flabellate, to 3 mm long and to 1 mm wide, and to 200 μm thick. Margins crenate to ±ragged, with wart-like aggregations of isidia. Upper surface vivid grey-blue when moist, paler when dry but still distinctly bluish, matt, minutely scabrid–areolate (×10 lens), isidiate. Isidia granular, wart-like, 0.1–0.2 mm tall, scattered to crowded marginally and crowded–aggregated centrally, concolorous with thallus or slightly darker at tips, forming a blue-grey, diffract-areolate crust. Apothecia and pycnidia not seen.
Chemistry : TLC−, all reactions negative.
N: Northland (Cavalli Is), Auckland (Anawhata). S: Otago (Rigney near Millers Flat). In lowland coastal forest in northern localities and common on willow bark along the Clutha River but probably more widely distributed. Recently recorded from eastern Australia (Jørgensen 2001: 127; McCarthy 2003c, 2006).
Australasian
Illustration : Jørgensen (1999a: 264, fig. 4).
Parmeliella aggregata is characterised by: the corticolous habit; the blue-grey thallus with marginal and laminal, wart-like, aggregated concolorous isidia forming a ± diffract-areolate crust. It has thinner lobes than P. gymnocheila, which also has coarse-grained soralia. It is also distinct from P. elixii which is a larger, foliose lichen with a scabrid, brownish or buff thallus (Pd+ orange) and marginal sorediate isidia.
