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1. The genus Actidium Fries Bulliardella (Saccardo) Paoli, 1905
The genus Actidium Fr. The genus Actidium was established (Fries 1823) to accommodate A. hysterioides Fr., a stellate mytilinidiaceous fungus found on Pinus and Picea in Europe, with two-celled, symmetric, ascospores, light olive to reddish-brown in color, faintly longitudinally striate in age (Barr 1990). Fries (1823) was the first to note its similarity to the genus Glonium in the Hysteriaceae, with hyaline to yellow, slightly asymmetric didymospores (Zogg 1962). Although only one species, A. nitidum (Ellis) Zogg, is known from temperate North America (Barr 1990), Zogg (1962) recognized an additional three species from conifers in Europe. Zogg (1962): “Fruitbody typically mussel- or clam-shaped (conchiform), st&ing on end, vertically, but sessile on the substrate & not at all stipitate. Alternatively, fruitbody like above in cross-section, but stellate or star-shaped or astral in outline, with three- or more branching rays. Fruitbody matt black, carbonaceous, brittle, fragile & thin walled; gregarious. Apex of fruitbody bearing a prominent keel, an extroverted longitudinal ridge running the length of the fruitbody, such that apex appears longitudinally acuminate. Asci clearly bitunicate, eight-spored. Ascospores two-celled, single septum, light olive to reddish brown in color; +/- constricted at septum, two cells +/- equal in size”. Barr (1990): “Ascomata superficial, gregarious, conchate or triangular or two to four grouped in radiating configuration, small to medium sized; apex cristate, opening by longitudinal slit; base rounded applanate; surface smooth, shining black, longitudinally striate; peridium firm, brittle, narrow, composed of several layers of elongate compressed cells, heavily pigmented externally. Asci cylindric.. Trabeculae sparingly branched & anastomosed, sparse. Ascospores light brown, oblong fusoid or straight or inequilateral, one septate median, slightly constricted; walls thin, smooth or delicately longitudinally striate; homogeneous; overlapping uniseriate in the ascus. Anamorphs not known, not formed in culture (Lohman, 1938; Zogg, 1962). On wood & twigs, occasionally leaves of gymnosperms, infrequent. Type species: Actidium hysterioides Fries. Notes: Zogg (1962) included Ostreionella Seaver (in Seaver & Chardon, Sci. Survey Porto Rico & Virgin Isl&s 8: 77. 1926) as a synonym of Actidium, but the type specimen of Ostreionella. fusispora Seaver has globose ascomata with an abrupt compressed short apical papilla & is instead more closely related to Ostropella in the Melanommataceae. Only one species, Actidium nitidum, is known from temperate North America. This species seems to be closely related to Actidium hysterioides but differs in not forming radiating groups of ascomata, in habit on members of the Cupressaceae rather than of the Pinaceae & in slightly narrower ascospores. The fine longitudinal striations on walls of ascospores have not been reported previously. Actidium Baccarinii (Paoli) Zogg is known from Europe & Actidium pulchra (Teng) Zogg from China. Both of these species have larger ascospores that the other two”.
Dichotomous Key to species of Actidium Fries A. Fruitbody star-shaped or astral when seen from above. Ascospores 11 – 14 x (1.5) 2 – 3 μm: = Actidium hysterioides Fr. B. Fruitbody mostly mussel- or clam-shaped (conchiform), not star-shaped. 1. Ascospores (9) 11 – 14 (16) x (1.5) 2 – 3 μm: = Actidium nitidum (Ellis) Zogg 2. Ascospores (16) 18 – 22 (24) x (3) 4 – 5 (6) μm: = Actidium baccarinii (Paoli) Zogg 3. Ascospores 23 – 28 x 6 – 7.5 μm: = Actidium pulchra (Teng) Zogg Detailed Dichotomous Key to species of Actidium Fries A. Fruitbody star-shaped or astral when seen from above. Ascospores 11 – 14 x (1.5) 2 – 3 μm: =Actidium hysterioides Fr. Syst. Myc. II, 1823, 596. Rare. Europe. Old wood of Pinus & Picea. B. Fruitbody mostly mussel- or clam-shaped (conchiform), not star-shaped. 1. Ascospores (9) 11 – 14 (16) x (1.5) 2 – 3 μm: = Actidium nitidum (Ellis) Zogg Ber. Schweiz. Bot. Ges., 1960, 70, 195-205. Rare. North America & Europe. Collected from the bark & wood of weathered Pinus, Picea & Juniperus. Important synonyms: Glonium nitidum Ellis ex Cooke et Ellis, 1879; Bulliardella nitida (Ellis) Lohman 1938; Psiloglonium nitidum (Ellis) Petrack 1953. Glonium nitidum Ellis, 1879 Ellis & Everhart (1892) for Glonium nitidum Ellis: “Fruitbodies densely gregarious, superficial, minute (0.25 – 0.5 μm long), lying parallel in the direction of the fibers of the bark, sub-conchiform, faintly striate; lips closed so as to form a narrow ridge or crest along the apex of the fruitbody. Asci cylindrical, sessile, 35-45 x 4 μm. Paraphyses if present not distinct (?). Ascospores uniseriate, clavate-oblong, uniseptate, hyaline, 6 – 7 x 2 – 2.5 μm. Collected from the inner surface of the loosened bark of cedar Cupressus thyoides on stumps, not too much decayed; fairly common around Newfield, NJ.” Barr (1990): “Ascomata gregarious, 200 – 400 μm long, 130 – 150 μm in diameter & in height. Asci 45 – 60 x 3.5 – 5 μm. Ascospores (6-) 7.5 – 10 (-12) x 2 – 3 μm, apex obtuse, base more acute; wall finely longitudinally striate. Distribution on twigs & leaves of conifers, north temperate zone. Collected from New Jersey on Thuja occidentalis. Note: Petrak’s (1953) combination in Psiloglonium was made on the basis of a collection from Florida. The small sizes of asci & ascospores suggest that Petrack had a different species according to Zogg (1962).” 2. Ascospores (16) 18 – 22 (24) x (3) 4 – 5 (6) μm: = Actidium baccarinii (Paoli) Zogg Ber. Schweiz. Bot. Ges., 1960, 70, 195-205. Rare. Europe. Collected from old wood of Pinus, Picea & Thuja. 3. Ascospores 23 – 28 x 6 – 7.5 μm: = Actidium pulchra (Teng) Zogg Ber. Schweiz. Bot. Ges., 1960, 70, 195-205. Synonym: Bulliardella puchra Teng 1936. China. |
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