SPECIMENS EXAMINED: NORTH ISLAND: AUCKLAND: N of Kaukapakapa, vic. Glorit, Atuanui State Forest, Mt Auckland, on Cyathea dealbata, 11 Sep 1980, G. J. Samuels & P. R. Johnston, PDD 49673; Waitakere Ranges, Anawhata Rd, on Cyathea dealbata, 9 Jun 1981, G. J. Samuels & P. R. Johnston, PDD 42047,* immature, anamorph on host.

Stromata breaking through the host epidermis, splitting it in a stellate manner (Fig. 1E), exposing the conidial state as white tufts, sometimes with host epidermis attached to its surface as white scales at an early stage. Stromata (375)438 ± 43(500) µm high, (500)657 ± 75(750) µm wide (n = 10), cylindrical to conical with almost flattened top, initially appearing white to light brown due to the attached host epidermis, black when fully emerged, with smooth surface, solitary. Ostioles finely papillate. Ectostroma 25-50 µm thick. Entostroma not seen. Perithecia detached and collapsed in mature material. Ascus apical rings (2.4)2.7 ± 0.2(2.8) µm high, upper width 2.8-4 µm, lower width 1.9- 2.8 µm (n = 6), without bulge at upper margin, J+, pale blue. Ascospores (13)14.6 ± 0.8(16.8) µm long, (6.7)7.5 ± 0.3(8.2) µm wide ( n = 45), inequilaterally ellipsoidal, dark brown, with straight germ slit, running over the whole spore length, some ascospores with a basal, 1 x 1 µm large, cellular appendage. Conidiophores variable in length, 2.5-5 µm in width, hyaline to light brown at base, as white tufts on young stromata, arising from parenchymatous cell tissue. Conidia 3-4 x 3 µm (n = 10), globose, hyaline to light brown.
ANAMORPH: Acanthodochium.

HOST: Cyathea dealbata.
MATRIX: Rachides.

Stromata e hospitis epidermide erumpentia, epidermidem stellae ad instar secedentia, (375)438 ± 43(500) µm alta, (500)657 ± 75(750) µm lata, cylindracea vel conica apice fere applanato, primo alba ad pallide brunnea ob hospitis epidermidem, nigra cum omnino erumpentia, superficie laevi, solitaria. Ostiola subtiliter papillata. Asci annulus apicalis (2.4)2.7 ± 0.2(2.8) µm altus, parte superiore 2.8-4 µm, inferiore 1.9-2.8 µm latus, margine superiore non protuberanti, iodo pallide coerulescenti. Ascosporae (13)14.6 ± 0.8(16.8) µm longae, (6.7)7.5 ± 0.3(8.2) µm latae, inaequilateraliter ellipsoideae, atrobrunneae, fissura germinativa recta, ascospora tota recurrenti praeditae. Ascosporae nonnullae appendice cellulari 1 1 µm dimensione praeditae. Status anamorphosis Acanthodochium.

ETYMOLOGY: Referring to the host plant, Cyathea spp.
NOTES: Astrocystis cyatheae has non-splitting stromata and is characterised by ascospores with a cellular appendage. No stromatic remnants were detectable on the host epidermis folded away, as described for other Astrocystis species with splitting stromata such as A. mirabilis Berk. & Broome. On very young stromata the anamorph was observed as white to cream tufts. Its morphology corresponds to Acanthodochium.
That a fern is the host for this Astrocystis species is remarkable, as all other species of this genus are known from monocotyledons. So far, xylariaceous fungi have not been reported on pteridophytes (Rogers 1979).
Astrocystis species with a spore size roughly similar to that of A. cyatheae and non-splitting stromata are A. hughesii Læssøe & Spooner, A. palmarum Læssøe & Spooner, A. rachidis (Pat.) K.D.Hyde & J.Fröhlich, Astrocystis selangorensis G.J.D.Smith & K.D.Hyde, and Rosellinia albocincta Petch. Astrocystis hughesii has smaller stromata and ascospores with a shorter germ slit that is less than spore length. Astrocystis palmarum has much larger stromata and ascospores lacking an appendage. Astrocystis rachidis has smaller ascospores without an appendage and smaller ascus apical rings. Astrocystis selangorensis has larger ascospores with a cellular appendage, and its stromata are softwalled; the ascus apical rings are also larger (Smith & Hyde 2001). Rosellinia albocincta Petch has larger stromata and smaller ascospores without appendages.

HOLOTYPUS (hic designatus): New Zealand, North Island, Auckland, N of Kaukapakapa, vic. Glorit, Atuanui State Forest, Mt Auckland, on Cyathea dealbata, 11 Sep 1980, G. J. Samuels & P. R. Johnston, PDD 49672.