Stem about 1/4 of an inch high, at first clothed with spongy down, then naked, longitudinally wrinkled; head ovate, or subelliptic, strongly compressed, obtuse, about 1 inch long, and ½ to 2/3 broad, sometimes giving off a second head at the base, minutely areolate, dotted with the slightly prominent ostiola. Asci slender; sporidia subelliptic, 1/2500 of an inch long

stipite brevi primum spongioso-velutino demum nudo rugoso, clavula obtusa ovata vel subelliptica valde compressa minutissime areolata, ostiolis prominulis punctato-aspera.

A very distinct species, resembling most X. lingua. Lév. True X polymorpha has the sporidia about 1/1000 of an inch long. The name indicates the resemblance of the head to a beaver's tail.

On dead wood, Colenso.

REPRESENTATIVE SPECIMENS EXAMINED: NORTHLAND: Hokianga County, Waipoua State Forest, vic. forest H. Q. along Waipoua River, on indet. wood, Samuels (83-509) et al., 11 May 1983 (PDD 45734); Hokianga County, vic. Mangamuka Bridge, Omahuta State Forest, vic. forest H. Q., on decorticated wood, Samuels (82-51) & Johnston, 14 Apr. 1982 (PDD 44288). COROMANDEL: Tapu-Coroglen Rd., track to Maumaupaki, elev. 450 m, on indet. tree, Samuels et al., 11 Jan. 1985 (PDD 47429). GISBORNE: Urewera National Park, Lake Waikaremoana, vic. Motor Camp, Ngamoko Track, on Beilschmiedia tawa, Samuels (83-481) et al., 30 May 1983 (PDD 45762); Urewera National Park, c. 15 km SE of Ruatahuna, along SH 38, Taupeupe Saddle, on Nothofagus menziesii (Hook. f.) Oerst., Samuels (82-301) et al., 3 Nov. 1982 (PDD 43802). TARANAKI: Mt Egmont National Park, track between Stratford and Dawson Falls, at base of small dead tree, Samuels (83-488) et al., 24 Apr. 1983 (PDD 45759). TAUPO: Tongariro National Park, Mt Ruapehu, on Nothofagus sp., Cunningham, Mar. 1929 (PDD 18950); T.N.P. on Phyllocladus aspleniifolius var. alpinus, Dingley, 20 Oct. 1949 (PDD 18948); T.N.P. Dingley, on Griselinia littoralis, Oct. 1949 (PDD 45392); Mt. Ruapehu, Whakapapa River, 3000 ft., on Pittosporum sp., Dingley, 20 Oct. 1949 (PDD 18955); Mt. Ruapehu, Whakapapa, on Pseudopanax colensoi, Dingley, 19 Oct. 1949 (PDD 18956); T.N.P., Station Bush, on Podocarpus hallii, Baker, 20 Jan. 1954 (PDD 18949). NELSON: Karamea, Huia River, on Nothofagus menziesii, McNabb, 20 Oct. 1959 (PDD 19802); Black Point, Murray Creek, on Nothofagus sp., Johnston, 31 Dec. 1980 (PDD 42080). BULLER: c. 33 km SE of Murchison P.O. on Murchison-Maruia Saddle Road, on indet. wood, Samuels (83-511) et al., 24 May 1983 (PDD 45735); 26 km S of Murchison, at a point where Pea Soup Creek joins Maruia River, on Murchison-Lewis Pass Road, on indet. wood, Samuels (83-537) et al., 26 May 1983 (PDD 45731); Nelson Lakes National Park, on ?Pittosporum sp., Samuels (83-512) et al., 25 May 1983 (PDD 45761). WESTLAND: Copeland Valley, Douglas Rock, on Pseudopanax colensoi, Cunningham, 31 Jan. 1947 (PDD 5139); Granville Forest, Orwell Creek, on Nothofagus fusca (Hook. f.) Oerst., Dingley, 1 Apr. 1963 (PDD 21948); Westland National Park, Fox Glacier, Lake Matheson, on ?Weinmannia racemosa, Samuels (83-473) et al., 7 Apr. 1983 (PDD 45764); Haast Pass, c. 58 km E of Haast junction along Robinsons Creek, on Nothofagus menziesii, Samuels (83-454) et al., 12 Apr. 1983 (PDD 45748); Westland National Park, Franz Josef Glacier, track to Lake Wombat, on indet. wood, Samuels (83-474) & Petersen, 10 Apr. 1983 (PDD 45763). NORTH CANTERBURY: Arthur's Pass National Park, eight collections on Nothofagus solandri (Hook. f.) Oerst. and indet. wood, Samuels et al., 19-20 May 1983 (PDD 45730, 45732, 45760, 45768, 45770, 45771, 45772, 46538). FIORDLAND. Doubtful Sound, on Nothofagus menziesii, Dingley, Feb. 1948 (PDD 45391). Eglinton Valley, Knob Flat, 1500 ft., on Nothofagus sp., Atkinson, Jan. 1964 (PDD 23859). SOUTHLAND: Alton Valley, Tuatapere, on Nothofagus menziesii, Dingley, 23 Feb. 1954 (PDD 45390); Catlins State Forest Park, Grahams Road, Haldane Scenic Reserve, on indet. tree, Samuels (85-75) et al., 17 Apr. 1985 (PDD 47417).

Stromata solitary to gregarious but not fasciculate; unbranched, cylindrical, clavate, lanceolate or broadly spathulate, (1-)3-4(-6) cm long x 3-25 mm wide x 2-5(-10) mm thick, tip acute to rounded, entire stroma fertile; sessile or seated on a barely differentiated, plane or slightly enlarged, glabrous or villous stipe to 7 mm long x 3-4 mm wide; brown to dull blackish brown. Surface splitting into distinct plates, each plate with 1-2 minute papillae; perithecia completely immersed, 400-500 µm diam. Asci 130-140 µm total length x (5.0-)5.5-7.0 (-8.0) µm, sporiferous portion (50-)70-85(-95) µm, cylindrical; apical ring J+, minute, 2-3 µm wide x 1-2.5 µm high; 8-spored, ascospores uniseriate with overlapping ends. Ascospores (8.0-)9.5-11.0(-14.0) x (4.5-)5.06.0(-6.5) µm; elliptical, inequilateral to nearly symmetric, dark brown, nearly opaque, slit obscure, probably full-length, straight, parallel to long axis of ascospore. Conidiophores in vivo forming a dense, 25-50 µm deep palisade over the stromal surface; comprising branched, colourless, smooth conidiophores, each branch terminating in a conidiogenous cell; conidiogenous cells (9-)11-15(-17) x 2-3 µm, cylindrical; condiogenous loci terminal, with a 0.5-1.0 µm wide refractive circular scar remaining after conidial dehiscence. Conidia (5.0-)5.3-7.7(-9.0) x (1.5-)2.0-2.8(-3.5) µm, oblong to clavate, colourless, smooth; each with a 1 µm wide, refractive or non-refractive, frilled, basal abscission scar.
CHARACTERISTICS IN CULTURE: Cultures grown 2 weeks at 20°C in diffuse daylight on OA 3-5 cm diam.; mycelium cottony, white to pale salmon with no black colouration on the surface of the agar; stromata arising from centre or margin of colony, or stromata not forming. Stromata 7-20 x 1-3 mm, cylindrical with tip acute or less frequently spathulate; at first entirely pale salmon, gradually becoming dark below, without distinctive hairs; most remaining sterile with conidia found only once in culture.

DISTRIBUTION: (numbers of specimens examined in parentheses). NORTH ISLAND: Northland (2), Coromandel (1), Gisborne (3), Taupo (9), Taranaki (1). SOUTH ISLAND: Nelson (9), Buller (4), Westland (8), N Canterbury (8), Fiordland (2), Southland (2).

HABITAT: On decaying wood of trees; most often on Nothofagus spp. and Weinmannia racemosa Linn. f., but also on the dicotyledonous trees Beilschmiedia tawa (A. Cunn.) Kirk, Pittosporum sp., Pseudopanax colensoi (Hook. f.) Philipson, Griselinia littoralis Raoul and on the gymnosperms Phyllocladus aspleniifolius (Labill.) Hook. f. var. alpinus (Hook. f.) Keng, Podocarpus hallii Kirk, and Dacrycarpus dacrydioides (A. Rich.) de Laubenfels.

Xylaria castorea is the most common Xylaria in New Zealand and is usually an inhabitant of Nothofagus forests. It was originally described as being the shape of a beaver's tail (Castor) but, in fact, the broadly spathulate form is less frequently found than the cylindrical form. The species is extremely variable, the most usual forms being cylindrical to lanceolate with an acute apex. All of these forms feature a distinctive plate-like cracking of the stromatal surface, a minute apical ascal ring, and very dark ascospores with a germ slit that is often difficult to discern. Cultures derived from all of these growth forms are identical.
Martin (1970) cultured South African specimens of what he believed to be X. castorea. Colonies were described as white; stromata were produced, but conidia were not observed. Isolates of X. castorea from New Zealand are salmon-coloured, thus leaving some doubt as to the identity of the South African collections.
Xylaria castorea is strongly allied to X. curta Fr. and X. feejeensis (Berk.) Fr. and, indeed, further study might show it to be only a form or subtaxon of the latter species. The anamorph and cultures described for X. curta (Rogers 1983) resemble those of X. castorea. Cultures of X. feejeensis from France are similar to those of X. castorea described herein except that the bases of stromata of the former are conspicuously villose and areas of colonies sometimes darken; conidia have not been observed (J. D. Rogers, unpublished).
X. castorea can be confused with X. cubensis (Mont.) Fr. Stromata of both of these species are of similar stature and both have ascospores of approximately the same size but these two species are not closely related (see above and Rogers 1984).