REPRESENTATIVE SPECIMENS EXAMINED: NORTHLAND: Three Kings Island, on Albizia lophantha (Willd.) Benth., Newhook, 7 Jul. 1956 (PDD 47068); Bay of Islands, vic. Russell, Moturoa Island, on ?Metrosideros excelsa Sol. ex Gaertn. Samuels (85-84) et al., 17 May 1985 (PDD 47422); Russell State Forest, Ngaiotonga Scenic Reserve, Kauri Grove Track, on Melicytus ramiforus J.R. & G. Forst., Samuels (85-82) et al., 16 May 1985 (PDD 47427); Hokianga County, Omahuta State Forest, Kauri Reserve, on Freycinetia baueriana var. banksii, Samuels(82-229) et al., 1 Jun. 1983 (PDD 43204). AUCKLAND: Oratia, on Pinus radiata D. Don; D. W. McKenzie, Aug. 1948 (PDD 45394) Marton, on decaying stump, Cunningham, Jul. 1927 (PDD 45423). WELLINGTON: Lake Papaetonga, on wood, Neill, 2 May 1923 (PDD 45407). NELSON: Abel Tasman National Park, track along coast between Marahau and Guilbert Point, on Pinus radiata, Samuels (82-194) et al., 16 May 1982 (PDD 43177). NOUTHLAND: Otautau, on dead wood, Rawlings, Nov. 1946 (PDD 5026).

Stromata solitary to gregarious, unbranched or rarely branched near base and then fasciculate, (1-)2-3(-4) cm long; fertile portion lanceolate, circular to elliptic in section, 2-3 mm diam.; stipe to 10 mm long x 1.0-1.5 mm diam., not sharply delimited from fertile portion, slightly wrinkled, glabrous or with fine brown hairs; at first with a cinereous coating on surface of stroma, the cinereous colouration eventually disappearing and then stromal surface becoming black, smooth or slightly wrinkled; peritheeia completely immersed, 300-400 µm diam., each opening through an inconspicuous papilla; internal tissue of stroma solid, white. Asci 150-210 µm total length x 5-9 µm, the sporiferous part 65-100 µm, cylindrical; apical ring J +, cylindrical, 2-3 µm wide x 3-4 µm high; asci 8-spored, ascospores uniseriate with overlapping ends. Ascospores (11-)13-16(-19) x (4.0-)5.0-6.0(-7.5) µm, inequilateral with one side flat and one side curved; elliptic in top view; one-celled or with inconspicuous cellular appendage (primary appendage) on one end, transparent brown; slit full length or less than full length and then 7-12 µm long, diagonally inserted, or parallel to long axis of ascospore, straight or broadly sigmoidal.
CHARACTERISTICS IN CULTURE: Colonies grown three weeks at 20°C in diffuse daylight on OA 5 cm diam., with pronounced concentric rings of slightly raised, yellow-tan to orange-tan mycelium alternating with broader bands of appressed white mycelium. Stromata not forming in culture.

DISTRIBUTION: (number of specimens examined in parentheses). NORTH ISLAND: Northland (5), Auckland (13), Wanganui (1), Wellington (3). SOUTH ISLAND: Nelson (1), Southland (1).

HABITAT: On bark and decorticated wood of angiosperms and gymnosperms but not found in Nothofagus forests.

Xylaria arbuscula was originally described from a greenhouse in Italy and has since been reported from various parts of the world. Dennis (1956) has listed probable synonyms and, later (Dennis 1961) accepted it as Xylosphaera mellisii (Berk.) Dennis [= Xylaria mellisii (Berk.) Cooke]. Because of the probability that several taxa will eventually be recognised (see below) we accept the better known name until additional studies can be done. Miller's description (1942) of X. arbuscula from Africa generally embraces our concept of the species.
Xylaria arbuscula from New Zealand is characterised by a thin, cinereous coating overlying the dark underlying stroma. This coat often disappears almost completely from older specimens. The ascospore germ slit is usually broadly sigmoidal, laterally inserted, and less than the full length of the ascospore. Ascospores sometimes bear a very inconspicuous cellular (primary) appendage on one end. The frequency of appendaged ascospores varies from collection to collection. Stromata from North µmerica, South µmerica and Europe usually show a more conspicuous cinereous or light tan outer layer which dehisces by shredding or peeling; ascospore germ slits are usually less than the full length of the ascospore and, in some cases, ascospores bear an inconspicuous cellular appendage (J. D. Rogers unpublished).
Cultures were made from four collections of X. arbuscula from New Zealand but these did not form stromata and remained sterile. Martin (1970) cultured X. arbuscula from Africa and reported only sterile stromata.