Development of the Ascocarp of Anthracobia melaloma

Abstract

SUMMARYAnthracobia melaloma is a small operculate discomycete which is found most frequently on burnt wood. It grows and fruits readily in pure culture. The species is heterothallic.Arichicarps are produced by both mating types when these are grown separately. Antheridia cannot be distinguished except when they are in contact with a trichogyne.Plasmogamy is effected by the coiling of the tip of the trichogyne around an antheridial hypha. One cell of the antheridial hypha, the one in contact with the very tip of the trichogyne, swells until it is almost spherical. The walls between this swollen cell (the antheridium) and the trichogyne break down permitting the interchange of nuclei and cytoplasm.The archicarp can be separated into 3 distinct regions just prior to the formation of ascogenous hyphae. The ascogonial cells have very large pores in the cross walls. The cells of the trichogyne can be distinguished by the amorphous structure of the protoplasm and the swellings in the cross walls of the 6 to 8 cells nearest to the ascogonium. The stalk cells are distinguished best by the broad hyphae branching from them.Ascogenous hyphae develop from 2, 3, or 4 ascogonial cells. These rapidly spread throughout the young apothecium and become septate. Branches arise from the cells of these primary ascogenous hyphae and 2 nuclei migrate into each of these branches. The lateral branches immediately bend over forming characteristic croziers, and conjugate division of the 2 nuclei in these laterals presumably occurs. Asci do not form immediately after the first croziers are developed. Instead, the nuclei in the penultimate cell usually divide conjugately again. This process of conjugate division in the penultimate cell may occur many times before an ascus is finally formed.The hyphae giving rise to the sterile portion of the apothecium develop from the stalk cells of the archicarp. These are broad hyphae which contain a darkly stained protoplasm and nuclei of the same size as the nuclei in the ascogonial and stalk cells.The formation of the cortex and paraphyses is the result of sympodial growth of the sheath hyphae as described by Corner (1929). The hairs are merely terminal cortical cells which differentiate further by elongation and by darkening and further thickening of the walls.