Cryphonectria parasitica

The fungus produces yellow-orange to reddish-brown stromata on bark, 0.5–3 mm in diameter and up to 2.5 mm high, embedded in the bark with the upper parts protruding. Conidiomata (pycnidia) are 100–300 μm in diameter, formed as irregular locules within stromatic tissue; composite stromata may form when several pycnidia coalesce into labyrinthiform structures >1 mm. Conidiophores are branched, with lateral and terminal branches bearing conidiogenous cells; conidia are ellipsoidal to bacilliform, 3–5 × 1.5–2 μm, hyaline and aseptate, extruded in yellow tendrils. Ascomata (perithecia) are globose to flask-shaped, 300–400 μm in diameter, dark brown to black, deeply immersed in the stroma with slender black necks up to 600 μm long. Asci are clavate to cylindric-clavate, 32–55 × 7–8.5 μm, 8-spored. Ascospores are hyaline, two-celled, ellipsoidal, 7–12 × 3.5–5.0 μm, sometimes constricted at the septum, with a gelatinous envelope.

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