Ascomata in vertical section with an upper wall up to 110 µm thick, comprising mostly brown to pale brown, slightly thick-walled, angular cells , but with dark brown, thick-walled cells along the outside of the wall, adjacent to the host tissue. The part of the wall adjacent to the ascomatal opening is lined with an extensive layer of thin-walled, cylindric, 3-5 µm diam., elements forming a palisade-like layer up to 100 µm wide in places. This layer is partially and irregularly covered with a deposit of yellowish, granular material. Lower wall 15-20 µm thick, of several layers of angular to cylindric cells, the outermost 1-2 layers of cells dark brown and thick-walled.

Paraphyses with anastomoses near the bases, 1.5-2 µm diam., more or less undifferentiated at apex, extending 10-20 µm beyond asci. Asci 140-180 x 17-20 µm, clavate, tapering to broad, subtruncate apex, wall undifferentiated at apex, nonamyloid, 8spored, spores confined to upper 90-110 µm of ascus, ascus development sequential. Ascospores 17-25 x 5-7.5 µm, elliptic, (0-)1 septate, hyaline, surrounded by a 2-5 µm thick gelatinous sheath.

Ascomata in vertical section with an upper wall 80-100 µm thick near the base, increasing to 300-500 µm thick near the ascomatal opening, comprising mostly brown to pale brown, slightly thick-walled, angular, 5-10 µm diam. cells, but the cells along the outer edge of the wall darker and thicker walled. The part of the wall adjacent to the ascomatal opening lined with a 30-65 µm wide, palisade-like layer of 35 µm diam., cylindric, thin-walled, hyaline cells. Lower wall 30-65 µm thick, comprising dark brown, thick-walled, 4-8 µm diam., angular cells, the outer rows of cells darker and thicker walled than the inner rows. A 10-20 µm wide layer of thin-walled, hyaline, cylindric cells separates the hymenium from the lower wall.

Paraphyses with anastomoses near bases, 1-2 µm diam., undifferentiated or irregularly circinate at the apex, extending up to 10 µm beyond the asci. Asci 210-330 x (18-)20-26 µm, clavate-stipitate, tapering to truncate apex, wall unthickened at apex, but often with small apical pore, nonamyloid, 8-spored, spores confined to upper 90-150 µm of ascus, ascus development sequential. Ascospores (26-)31-46 x 6-10 µm, oblong-elliptic, 0-3 septate, hyaline, surrounded by a 1-2 µm thick gelatinous sheath.

ETYMOLOGY: refers to host substrate.

NOTES: C. nothofagi, with phragmosporous ascospores, keys out to the genus Xyloschizon in Darker's (1967) key to the Rhytismataceae. However, Darker (p. 1415) noted that Xyloschizon appears to be segregated from Colpoma simply on the basis of ascospore septation, and as such is of doubtful validity. I do not consider ascospore septation a useful character at the generic level in the Rhytismataceae.

Ascomata in vertical section with a poorly developed upper wall. The part of the wall adjacent to the hymenium comprises 2-3 rows of hyaline, cylindric, 2-3 µm diam. cells, lined with a layer of hyaline, cylindric, periphysis-like cells, forming a layer up to 20 µm wide. The part of the wall which covers the hymenium before the ascomata open is 10-15 µm thick, made up of 2-3 rows of brown, thick-walled, angular cells. A darkened lower wall is lacking, the hyaline, hyphal tissue of the subhymenium resting directly on the partially broken down host tissue.

Paraphyses with anastomoses near the bases, 1-2 µm diam., with several short side branches near apex, forming a tangled epithecium, extending 20-30 µm beyond asci. Asci 100-120 x 11-15 µm, cylindric, rounded to subtruncate at apex, wall undifferentiated at apex, 8-spored, spores extending almost to base of ascus, ascus development sequential. Ascospores 20-26 x 5-8 µm, oblong-elliptic in face view, characteristically slightly curved in side view, 0-septate, hyaline, no gelatinous sheath.