Asci 8-spored, (105-)113-142(-160) x 7-9 µm, cylindrical to narrowly clavate, tapering toward the base, indistinctly pedicellate; pore J + Melzer's, obconical, tapering slightly to base, 1-1.5 µm long x 1.5-2 µm wide at top; ascal wall uniformly thick; ascospores in the upper (44-)57-103(-115) µm of each ascus, partially biseriate to uniseriate with overlapping ends. Ascospores (10-)15-20(-23) x (2.5-)3-4(-5) µm, hyaline, elliptical to subfusoid, straight or slightly inequilateral, with 1-8 guttules completely filling each ascospore, uniformly thin-walled, smooth. Paraphyses equal to or extending beyond asci by 10-25 µm, unbranched or branching along the length, 2-3 µm wide, tip clavate to subglobose, 3-5 µm, light brown, tips encrusted in a continuous layer of amorphous brown material; brown material becoming red in 3% KOH. Subhymenium well developed, up to 50 µm wide, not sharply delimited from medullary excipulum, consisting of a compact region of 3-5 µm wide, smooth, light brown hyphae; irregularly shaped deposits of brown pigment scattered throughout subhymenium. Medullary excipulum obconical when hymenophore discoidal, or nearly cylindrical when hymenophore cylindrical, continuous with ectal excipulum and medullary tissue of stipe, consisting of a compact region of vertically oriented, 3-5 µm wide, septate, branched, non-pigmented hyphae. Ectal excipulum ca. 250 µm wide at point where stipe joins hymenophore, tapering to ca. 60 µm wide at margin, outer ectal excipulum 30-40 µm wide, consisting of chains of angular cells 15-25 x ca. 10 µm with walls ca. 1.5 µm thick and dark brown, cells built up at points and forming columns 25-75 µm high; outer ectal excipulum continuous down stipe and over surface of umbilicate depression at apex of cylindrical hymenophore, covered with brown amorphous material; inner ectal excipulum 30-75 µm wide, consisting of a compact region of hyphal cells 15-45 µm long x 4-5 µm wide, arranged with long axes parallel to each other and to surface of receptacle, non-pigmented; cells at edge of margin ± angular in outline, 15-25 µm in greatest dimension, dark brown, forming flat, triangular teeth around hymenium of discoidal apothecium. Stipe solid, consisting of rind and medulla; rind ca. 30 µm wide, consisting of compacted chains of angular to circular, dark brown cells ca. 10 µm in greatest dimension with walls 1.5-2.0 µm thick, built up at points and forming columns 30-60 µm high; cortex of stipe continuous with outer cortex of stroma; covered with brown, amorphous material; medulla of stipe consisting of vertically oriented, light brown hyphae with cells 40-50 µm long x 8-15 µm wide, continuous with medulla of stroma.

Sclerotium and stipe base (and synnema) continuous; rind not ruptured by stipe base. Sclerotium appearing as a swelling ca. 3 mm diam. at base of stipe and synnema. Rind 75-112 µm wide, comprising 3 zones. Outermost zone 15-40 µm wide, of dark brown, thin-walled textura angularis to textura globulosa arranged ± in chains perpendicular to the sclerotial surface, giving rise to ± pyramidal mounds 15-30 µm long of globose brown cells on the rind surface; middle zone 15-30 µm wide of hyaline to light brown walled angular to inflated cells, 10-15 µm diam., lacking definite orientation with reference to the sclerotial surface; inner zone 15-25 µm wide of inflated angular to globose, light brown-walled cells, 10-15 µm diam. with irregular intercellular deposits of dark brown material. Cortex an extremely compact zone ca. 150 µm wide of narrow, pale brown, possibly gelatinous-walled textura intricata, cells 2-3 µm wide. Medulla of loosely packed textura intricate to textura oblita, cells 4-10 µm broad, walls 1 µm thick; no host tissue incorporated into cortex or medulla. Conidiomata arising at the base of the apothecial stipe or on a separate conidiomatal stipe which then arises directly from the sclerotium., up to 1.5 mm long, cylindrical, 100-250 µm diam. or flask-shaped and ca. 500 µm diam. at the widest point, each bearing a single, terminal globose to subglobose, 100-150 µm diam. head covered with a palisade of phialides. Head consisting of a convex hymenium and a central stromatic core; hymenium consisting of a compact, uniform palisade of phialides and marginal hyphae forming at the point where the head joins the stipe, entire hymenium covered with brown, amorphous material. Conidiogenous cells phialidic, phialides cylindrical, 13-20 x 2-3 µm, straight, smooth, brown, monoblastic, apex thickened, collarette not flared; marginal hyphae cylindrical with rounded tips, 10-15 x 6-9 µm, multiseptate, smooth, brown; marginal hyphae and phialides arising from a central stromatic core. Conidia ellipsoidal, 3-4 x 1.5-2 µm, lacking a basal abscission scar, unicellular, hyaline; central stromatic core consisting of textura angularis, cells 5-7 µm in greatest dimension, brown, many filled with amorphous brown material; cells of central stromatic core continuous with medulla of stipe. - Stipe consisting of cortex and medulla; cortex consisting of a ca. 30 µm wide layer of angular, dark brown cells 10-15 x 8-10 µm, arranged in short chains, tip cells of each chain rounded, forming columns at points, covered with amorphous brown material; cortex of stipe continuous with cortex of apothecial stipe or cortex of discrete conidiophorous stipe respectively; medulla of conidiomata 30-50 µm wide, consisting of hyphal cells 30-50 µm long x 5-6 µm wide with long axes arranged parallel to long axis of stipe, walls 1-1.5 µm thick, light brown, continuous with medulla of apothecial or conidiophorous stipe respectively.

The hymenophore of Sclerocrana atra has two distinct aspects, one discoidal and the other capitate. Although these appear to be quite different morphologically, they are anatomically identical. In one of the collections cited above the hymenium was partially wrapped around and fused to the apex of the stipe, thus appearing to be intermediate between the two morphologies. Because features of anatomy of the hymenophore and conidiomata and morphology of asci and ascospores are the same in the two morphological types and because both types have been found in the same locality, we believe that the morphologically different hymenophores fall within the normal variation of this peculiar species.

In its morphology and anatomy, S. atra seems to straddle the boundary between the Sclerotiniaceae and the Dermateaceae. The complex rind structure and well-defined cortical zone of the sclerotium have no precedent in the Sclerotiniaceae. It is possible that this "sclerotium" represents not a sclerotial anamorph but rather a complex stipe base that does not function as an independent morph. Nevertheless, the complex stromatal structure compares with that in the Sclerotiniaceae (KOHN, 1979). The teleomorph, based on its dark pigmentation, and angular cells seems more dermateaceous than sclerotiniaceous but based on the stroma we provisionally place this species in the Sclerotiniaceae. Within the Sclerotiniaceae this species is similar to Scleromitrula ushuaiae (REHM) GAMUNDI and S. viridis GAMUNDI. Scleromitrula ushuaiae produces pycnidial locules within the stroma (GAMUNDI, 1976; KOHN & NAGASAWA, 1984).

The anamorph of S. atra cannot be accommodated in any known anamorph genus. In the compact, palisadal arrangement of dark phialides the sporodochial genera Bloxamia BERKELEY & BROOME and Cystodendron BUBAK, both anamorphs of discomycetes (HENNEBERT & BELLEMERE, 1979), are suggested but conidia of these two genera are produced within tubular phialides.