Ascocarp Development in Mamianiella Coryli Var. Spiralis

SUMMARY

Mamianiella coryli var. spiralis was found in living leaves of Corylus cornuta. Following infection, hyphae occur within the cells of the upper epidermis, palisade meophyll and spongy mesophyll, as well as in the intercellular spaces of the spongy mesophyll. An individual stroma develops when intercellular hyphae in the spongy mesophyll proliferate into a loosely-organized prosenchyma. These hyphae destroy the host cells involved, extending from approximately the bottom of the palisade mesophyll to the inner face of the lower epidermis. Except in the vicinity of the palisade mesophyll, the periphery of this prosenchymatous zone differentiates into a compact, carbonaceous layer, also prosenchymatous. A filament of the inner, delicate stroma enlarges to become an archicarp while contiguous hyphae form the peridium. Peridial elements at the apex of the ascocarp grow out to form the neck which pushes through the carbonaceous stroma. The terminal cells of the archicarp comprise the ascognium which proliferates into the ascogenous elements and apparently into tne central pseudoparenchyma as well. These tissues continue to proliferate as the asocarp expands; the ascogenous elements form a hymenial zone at the periphery of the centrum, the balance of which is occupied by the pseudoparenchyma. At this stage, the ascogenous system comprises aseptate multinucleate branching hypae, as well as elements occurring either singly or in short chains. Single elements form croziers. Development of the perithecial cavity is due to breakdown of the central pseudoparenchyma whose remnants persist among the ascogenous elements as paraphysoidal bands. The pattern of ascocarp development in M. coryli is similar to that found in Gnomonia species, thus affirming Barr's inclusion of Mamianiella in the Gnomoniaceae. However, with reference to Barr's classification of this family, Mamianiella should be included with the Stegophoroideae rather than Mamianioideae, since its stroma is not (as in Mamianioideae) pseudoparenchymatous, but (as in Stegophoroideae) prosenchymatous.