Flora of New Zealand Series

Holotype: New Zealand. Wellington, between Owhiro Bay and Runaround, "on (siliceous) rocks just above H(igh) W(ater) S(pring tide level)", 19.ix.1970, N.M. Adams s.n. – WELT L1354.

Description : Thallus subepilithic to epilithic, effuse, dull medium-green to greenish black, smooth, rimose only around perithecia, 10–30(–50) μm thick. Prothallus not apparent. Photobiont green, cells broadly ellipsoidal to globose, 5–9(–10) × 5–8 μm. Perithecia compound, sessile, constricted at base, very numerous, usually solitary, often paired or in clusters or rows of 3–4, (0.28–)0.35(–0.42) mm diam., apex flattened or concave, ostiole inconspicuous, depressed. Involucrellum black, entire, 60–100 μm thick, surface smooth or rugulose. Centrum globose, 0.16–0.25 mm diam, IKI+ red-brown. Exciple brown-black, 25–32 μm thick. Periphyses simple, 24–35 × 1.5 μm. Paraphyses soon disappearing. Ascospores simple, colourless, ellipsoidal to broadly ellipsoidal, massed or irregularly biseriate in ascus, apices rounded, 9–12(–16) × 6–7(–8.2) μm, contents clear to minutely granular.

N: Northland (Poor Knights Is), Wellington. On intertidal rocks.

Endemic

Illustration : McCarthy (1991: 286, fig. 1).

Verrucaria sessilis is characterised by: the coastal rock habit; superficial perithecia that become markedly constricted at the base, together with comparatively small ascospores and a dark, effuse thallus (McCarthy 1991e, 1992b).