Apothecia sparsa, superficialia, stipitata, disco plano, luteo, 1 mm. lato; cupula applanata, atra, longitudinaliter fibrillose, margine dentibus coronata; stipes brevis, atris, in cupulam abiens. Asci cylindraceo-clavati, octspori, 90-95 x 8-9 µ, apice jodo non tincti; ascosporae monostichae, fusoideo-ellipsoideae, 2-4-guttulatae, hyalinae, 14-17 x 4-5 µ; paraphyses filiformes, apicem versus incrassatae.

H. metrosideri is structurally not unlike H. scutula, with flesh of loosely woven hyaline hyphae, 8-10 µ wide, and excipulum of compact parallel hyphae of similar size, lying at a low angle to the surface, covered by a thin web of more slender hyphae pulled somewhat apart into a mesh-work as the apothecium expands on wetting. These surface hyphae, 4-6 µ wide, are blackened by a granular deposit. There is in this a close resemblance to the structure of H. spadiceo-atrum (Mont.) Sacc., on Gunnera scabra in Juan Fernandez, but in the latter the ascospores are only 9-10 x 3 µ and the surface hyphae have a reddish-brown granulation and yield a purple solution in KOH.

In foiiis Metrosideri (Myrtaceae), Waiatarua, Waitakera Ra., Auckland, 29.5.1958, Dingley 19040 (typus).

Spores 14-17 x 4-5 µ.

[Notes from Kew Type specimen, PRJ 2010] Other collections in the Kew packet include a specimen from Ann Bell on Nothofagus menziesii leaves (a single apothecium); Horak 67/121 Helotium near metrosideri on Elaeocarpus hookerianus leaves; duplicated from PDD 19379. Images of the Horak Specimen. Apothecia with look of Lanzia 'aureus', assoc with extensive blackened patches on the fallen leaves;

NEW ZEALAND: Auckland, Waiatarua, Waitakere Ranges, on leaves of Metrosideros sp., 29 v 1958, leg. J.M. Dingley, ex P.D.D. 19040 (Holotype of H. metrosideri, K); on leaves of Metrosideros robusta, 23 vii 1958, leg. J.M. Dingley, ex P.D.D. 19379.

STROMA substratal, visible on both leaf surfaces as dark lines delimiting areas surrounding a single apothecium, and as dark areas at the base of the apothecia. APOTHECIA scattered or gregarious, hypophyllous, stipitate, erumpent through the epidermis which is split into 5 or 6 conspicuous erect or reflexed dark tooth-like lobes. DISC 0.7-1.0 mm diam., convex or plane, smooth, pallid with an olivaceous tinge. RECEPTACLE reflexed, pale, covered by a conspicuous meshwork of dark brown hyphae extending beyond the margin to form a dentate fringe to the disc. STIPE central, cylindric, dark brown to blackish, shorter than disc diam. ASCI 8-spored, cylindric or cylindric-clavate, narrowed below to a very short stalk, apex broadly conical or truncate, the pore only faintly outlined blue in Melzer's reagent, 80-95(-108) x 8-10 µm. ASCOSPORES hyaline, fusoid, inequilateral, often slightly curved, non-septate, containing a row of 3-5 large guttules, obliquely uniseriate or irregularly biseriate, 13.0-17.0 x 3.5-4.8, mean 15.2 (SD 0.9) x mean 4.2 (SD 0.3) µm. PARAPHYSES filiform, simple, 1.0-1.2 µm diam., enlarged above to a clavate or sometimes capitate apex, 3.5-5.0 µm diam., containing pale yellow granules of pigment, exceeding the asci by 5-8 µm. SUBHYMENIUM not clearly differentiated, composed of loosely woven hyaline hyphae 3-5 µm diam. MEDULLARY EXCIPULUM a narrow layer 30 µm thick at the base of the receptacle, narrowed to the margin, composed of parallel, subhyaline or pale brown hyphae 3-4 µm diam. In the stipe the hyphae are broader, 6-9 µm diam., vertically arranged, narrower towards the ectal layer. ECTAL EXCIPULUM composed of large prismatic cells with thickened walls, 15-20 x 9-14 µm in the receptacle, in rows at a very low angle to the surface. On the stipe the ectal cells are longer and narrower, 20-30 x 4-7 µm forming a layer not clearly differentiated from the medullary tissue and frequently with the pigment deposited in irregular granules. Ectal layer thin, 1-3 cells thick on the receptacle, 20-25 µm thick, giving rise at the surface to dark brown hyphae 4-7 µm diam. with clavate tips 6-10 µm diam., strongly encrusted throughout with dark brown pigment. Surface hyphae more densely developed at the margin and extending beyond the disc as a dentate marginal fringe. Those on the receptacle surface irregularly pulled apart as the apothecium expands to form an irregular, very conspicuous meshwork; those on the stipe narrower, 2.5-3.0 µm diam., the outermost excipular hyphae also pigmented forming a dark surface layer 5-8 µm thick. At the stipe base, diverging, dark brown, septate hyphae 3-4 µm diam., bind with the upraised epidermis to form the conspicuous dark tooth-like lobes surrounding the stipe base.

On dead leaves of Metrosideros sp. and M. robusta (Myrtaceae). Auckland, New Zealand.