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Remarks (public):For a complete description including images see 
Remarks (internal):Two varieties of this species exist. They may be easily distinguished with the naked eye by the external appearance of their conidiomata. Lirula nervisequia var. nervisequia produces very few conidiomata, and these rarely fuse together, so that the upper side of the needle appears to the naked eye to carry no fruitbodies. By comparison, L. nervisequia var. conspicua Darker bears large numbers of conidiomata which normally fuse to form a large multi-locular fruitbody, often running the whole length of the needle.
Description type:Non-original description 
Description:Lirula nervisequia (DC.: Fr.) Darker, Canadian Journal of Botany 45: 1420, 1967.
Hypoderma nervisegaum DC., Flore francais 6: 167, 1816.
Hysterium nervuisequium (DC.: Fr.) 1823.
Lophodermium nervisequium (DC.: Fr.) Chev., 1826.
Hypodermopsis nervisequia (DC.: Fr.) O. Kuntze, 1898.
Hypodermella nervisequia (DC.: Fr.) Lagerberg, 1910.
Hypodermella lirelliformis Darker, 1932.
Ascocarps embedded in browned needles, only on the lower side, when dry dark grey, with a poorly-defined outline, linear, running along the raised mid portion of the needle lower surface, up to about 10 mm long, opening by a single longitudinal split, lips absent; in mid-point vertical section intra-epidermal, i.e. with the upper walls and contents of the epidermal cells above the clypeus, and the lower walls of the epidermal cells below the lower wall, the clypeus being well-developed and extending to the edge of the ascocarp on both sides, the lower wall being unblackened. Asci unitunicate, iodine negative, maturing sequentially, saccate, 150-200 x 24-30 µm, containing eight spores arranged more or less fasciculately. Ascospores hyaline, aseptate, smooth, filiform, 75-90 x 3-4 µm, enveloped in a mucous sheath 3-4,5 µm thick. Paraphyses hyaline, filiform, smooth, septate, unbranched, enveloped in a mucous sheath. Conidiomata preceding and accompanying the ascocarps, but only on the upper side of the needle, brown, the same colour as, or slightly paler than the needle, elliptical to elongated elliptical, in some cases (not illustrated here) fusing to form multilocular fruit-bodies (see notes below), when single 200-400 µm long, opening by ostioles, also by a longitudinal split to one side of the fruitbody, the split being often lined with blackened fungal cells; in mid-point vertical section intraepidermal, with a blackened upper wall one cell thick sometimes present. Conidiogenous cells cylindrical to slightly tapered, hyaline, smooth, 6-8 x 1-1,5 µm, proliferating enteroblastically percurrently, phialides. Conidia hyaline, aseptate, smooth, ellipsoidal, 2-3 x 1 µm. Zone lines generally absent, but in some conditions a blackened zone line is produced at the base of the needle, where its peg joins the twig.
Hosts: Abies alba, A. cephalonica, A. pectinata.
Disease: Needle cast of fir. Lirula nervisequia is locally serious in Europe (but not in Great Britain) as a cause of defoliation of A. alba. Discoloration does not appear until the leaves are two years old, i.e. at the beginning of their third year. On A. cephalonica the fungus seems to be purely saprophytic.
Geographical distribution: Europe (Austria, Czechoslovakia, Denmark, France, Germany, Greece, Hungary, Italy,
Rumania, Sweden, Switzerland).
Physiological specialization: None reported.
Transmission: By air-borne ascospores in wet or humid conditions.
Literature: Hartig, Wichtige Krankheiten der Waldbaume, Springer, Berlin, 1874; reprinted as Phytopathological Classics No. 12, translated into English by Merrill, Lambert & Liese, American Phytopathological Society, 1975.
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