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).

[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;