The anatomy of the mature perithecium in Sordaria humana and its significance for fungal multicellular development

Abstract

The three-dimensional anatomy of mature perithecia was studied by light and scanning electron microscopy. Freeze-fractured material which was cither frozen-hydrated or freeze-dried received particular attention. The results illustrate certain basic features of fungal multicellular development. All perithecial cellular elements have been classified as either hyphal (hyphallike) or coherent. Elements of the neck peridium, basal peridium, and centrum pseudoparenchyma are coherent. Other elements are hyphal (hyphallike). The internal hyphallike elements are tightly packed within the coherent tissues and surrounded by mucilage. The perithecial "cavity" does not contain empty spaces. All stages of ascus development were observed. Highly vacuolated, irregularly branched hymenial and lateral paraphyses are present and may function as space-making and space-filling structures within the perithecium. The periphyses differentiate into the neck peridium and probably also grip asci prior to ascospore discharge. The basal peridium has one layer and the neck peridium has two layers. The centrum pseudo-parenchyma is flattened in mature perithecia. Comparisons are made with the modes of development undergone by other organisms.