Menegazzia castanea P.James & D.J.Galloway
* Account prepared by P.W. James (BM).
Holotype: New Zealand. Otago, Old Man Range. On sheltered side of schist outcrop, with Neuropogon ciliatus and Thamnolia vermicularis, 1200 m. P.W. James, 1 February 1963. BM!
Thallus firmly attached at margins, ± loosely attached centrally, forming radiating, regular rosettes, often becoming irregular and coalescing to cover extensive areas of substrate, to 20 cm diam., saxicolous, sometimes spreading over soil and adjacent lichens and mosses. Lobes numerous, marginally radiating, rather regular, small to medium, 2-4 mm wide, often obscured centrally by numerous, short, imbricate, congested lobules, margins contorted, entire, often notched, often, extensively blackened, pigment spreading to centre of lobes, hollow, markedly inflated, lower side of internal cavity black. Upper surface pale grey-brown or fawn, apices and sometimes lateral lobes suffused brownish, ± maculate, with black or dark brown lines or patches, often denser centrally (×10 lens), smooth or puckered (especially centrally), shining and faintly white-maculate or reticulate towards lobe ends, sorediate. Perforations sparse to scattered, small, 0.2-0.5 mm diam., rounded or irregular, margins not elevated. Soralia pustular, arising as swellings on upper surface with eventual rupture and folding back of cortex to form coarse or finely abraded, efflorescent, proliferating, granular-sorediate clusters, coalescing centrally, soredia greyish-fawn, pale when abraded. Lower surface black, brown or red-brown marginally, extensively puckered. Apothecia rare, scattered or contiguous in groups, small, 2 mm diam., adnate, cupuliform, margins elevated, crenulate-striate, disc red-brown to brown, epruinose. Epithecium pale red-brown or brown, with numerous small granules. Hymenium c. 100-130 µm tall. Asci 2-spored. Ascospores ellipsoid, 39-44 × 21-23 µm. Chemistry: Stictic, constictic and menegazziaic acids and accessory substances; medulla K+ yellow → orange, C-, KC+ orange, Pd+ orange.
S: Canterbury to Southland, east of Main Divide, alpine or subalpine on rock, 1000-2000 m. C: M:
Australasian
M. castanea is the sorediate counterpart of M. aeneofusca. The development of soredia resembles that of M. nothofagi (which may also occur in similar habitats), that is in the bursting of coarse swellings from the upper surface producing coarse, granular soredia surrounded by torn edges of the upgrowth. M. nothofagi has narrower lobes (0.5-0.8 mm), with a plane or concave surface and is mostly green in colour. Although mainly saxicolous M. castanea may also grow on soil or among mosses on soil.
