Subiculum persistent, dark brown, wiry, with synnemata. Stromata (750)850 ± 60(950) µm high, (700)1007 ± 194(1250) µm wide (n = 10), cupulate, subglobose to globose, dark brown, black around the ostioles, solitary, often crowded, when young completely embedded in the subiculum, gradually emerging while growing. Ostioles finely papillate. Ectostroma 75-100 µm thick, black, hard, brittle. Entostroma cream, confined to base, absent in mature material. Perithecia detached and collapsed in mature material. Ascus apical rings (4.8)5.9 ± 0.5(6.7) µm high, upper width 4.3-4.8 µm, lower width 2.8-3.8 µm (n = 10), J+, dark blue. Ascospores (17.3)20.5 ± 1.4(24) mm long, (6.7)7.6 ± 0.5(8.6) µm wide (n = 60), inequilaterally ellipsoidal with one flat side, often broadly rounded, dark brown, with straight germ slit running over the whole spore length. Synnemata up to 1000 µm high, conidia 7-8 x 3-4.5 µm.
ANAMORPH: Dematophora.

HOST: Hoheria populnea.
MATRIX: Decorticated, heavily decomposed wood.

Subiculum perdurans, atrobrunneum, filo metallico simile, synnemata ferens. Stromata (750)850 ± 60(950) µm alta, (700)1007 ± 194(1250) µm lata, cupulata, subglobosa vel globosa, atrobrunnea, ostiola circa nigra, singularia, saepe conferta, in subiculo omnino dum juvena immersa, aetate paulatim emergentia. Ostiola laeviter papillata. Annulus apicalis asci (4.8)5.9 ± 0.5(6.7) µm altus, parte superiore 4.3-4.8 µm et inferiore 2.8-3.8 µm µm latus, iodo valde coerulescenti. Ascosporae (17.3)20.5 ± 1.4(24) µm longae, (6.7)7.6 ± 0.5(8.6) µm latae, asymmetrice ellipsoideae et lato applanato, late rotundatae, atrobrunneae, fissura germinativa recta totam ascosporam recurrenti praeditae. Status anamorphosis Dematophora.

ETYMOLOGY: In honour of the mycologist S. J. Hughes, who collected the paratype.
NOTES: Rosellinia hughesii is characterised by its Dematophora anamorph and the shape and size of its ascospores with a long germ slit. Only ascospores without slimy sheath or caps were observed. This, however, may be due to the age of the material. It would not be surprising in the future to find material having ascospores with slimy sheaths or caps.
Most Rosellinia species with a Dematophora anamorph have long, slender ascospores with a very short straight germ slit as seen in R. arcuata. In this respect, R. hughesii resembles R. buxi Fabre, as both have similar ascospore shapes. The latter, however, has larger ascospores with a short germ slit, taller stromata, and smaller synnemata. The size of conidia is almost the same in both species (Petrini 1993). Rosellinia hughesii differs from R. gisbornia by its persistent dark brown subiculum with the Dematophora conidial state, larger stromata, and smaller ascospores, and from R. mammaeformis by the larger stromata, persistent subiculum, and anamorph.

HOLOTYPE: South Island: Mid Canterbury: Kaituna, Waiwera County, on unknown host, 31 Oct 1963, H. C. Smith, PDD 22120; PARATYPE: South Island: Mid Canterbury: Kaituna Valley, Banks Peninsula, on Hoheria populnea, 15 Oct 1963, S. J. Hughes, PDD 21799.