Arnium caballinum  

Stromata: absent.

Ascomata: 350-600 µm diam, pyriform, the body ± globose, semi-immersed to almost superficial, matt black, covered with greyish brown mycelial hairs and irregular amorphous melanized patches at the base of the neck, the neck conical to cylindrical, to 500 µm in length, periphysate, often with a few short rigid cylindrical hairs. Peridium membanaceous, composed of three layers; the outer of pale brown irregular rather thin-walled textura angularis with cells to 10 µm diam, the innermost layer composed of ± hyaline flattened cells. Interascal tissue of wide, tapering paraphyses, sometimes inflated between the septa. Asci 220-300 x 32-44 µm, sometimes up to 75 µm wide when the ascospores are completely mature, cylindric-clavate, with a tapering stalk, fairly thin-walled at all stages, the apex rounded to truncate with a wide funnel-shaped J- apical ring, 8-spored. Ascospores arranged biseriately, 31-40 x 18-24 µm, ellipsoidal, sometimes inaequilateral, dark brown and thick-walled, smooth, aseptate, with a single apical germ pore, and prominent persistent tapering elongate subapical and subbasal appendages 50-95(-120) x 6-10 µm, round and canaliculate in cross-section.

Anamorph: unknown.

No GB material seen; data taken from Lundqvist (1972).