Development and Cytology of Sordaria Humana

Abstract

A coiled, septate, multinucleate ascogonium or its parent hypha produces branches that enfold the ascogonium and produce a small ball of cells with the ascogonium in the center. The outer layers of cells differentiate into the perithecial wall. As the radius of the perithecium doubles, the number of wall cells increases twoto threefold per section and each cell expands sufficiently in volume to maintain the spherical shape of the perithecium. Plectenchyma cells of the centrum produce paraphyses which grow upward into a subapical cavity that is present before the paraphyses originate. Above the cavity a dome-shaped region of meristematic cells produces the neck, ostiole, and periphyses. The ascogonium does not increase in size when the perithecium enlarges. Ascogenous hyphae develop from the ascogonium after the neck and ostiole and paraphyses have begun to form. Terminal branches of ascogenous hyphae produce croziers, which in turn produce asci. Cytology of the ascus is much like that in other pyrenomycetes and includes a diffuse diplotene stage. Spores are initially uninucleate, later binucleate. The fungus is homothallic. The haploid chromosome number is seven.