Flora of New Zealand Series

Thallus to 3.5 cm tall. Pseudopodetia simple or sparingly branched, tapering from base to apex, decorticate and rather pruinose. Phyllocladia on short, thick stems, rounded peltate, becoming warted-convolute with a prominent dark greenish-grey centre and pale margins, small and crowded at apices of pseudopodetia, larger and more dispersed towards base of pseudopodetia. Cephalodia ± sessile, infrequent, dark green, black or brown, rather amorphous, gelatinous, shining, clustered at base of phyllocladia towards base of pseudopodetia. Apothecia rare in New Zealand material, mainly at apices of pseudopodetia, to 1 mm diam., disc pale brown with a concolorous prominent margin when young, occluded at maturity. Ascospores 3-5(-6)-septate, (25-)30-50(-55) × 2.5-3.5 µm. Chemistry: Atranorin and stictic acid; ± norstictic acid.

N: Rangitoto, Coromandel Peninsula, Ruapehu, Kaimanawa Ra., Egmont. S: Nelson (Waiau Pass, Mt Technical), Canterbury (Hills Peak, Mt Misery near Cass). On volcanic soils, lava, rarely in subalpine grassland, s.l. to 1500 m.

Cosmopolitan

S. vesuvianum is distinguished from all other species of Stereocaulon by characteristic morphological and chemical differences viz: the clustered, peltate phyllocladia with darker centres and pale margins, and the presence of stictic acid in the medulla. In New Zealand it shows considerable variation, from erect, ± conical clumps or tufts, to a scattered closely appressed crust of phyllocladia on very reduced pseudopodetia.