Perithecial Development in Pleospora trichostoma

Abstract

Perithecia of Pleospora trichostoma arise as small knots of multinucleate hyphae in agar cultures. Mature asci are produced only after 3-4 months at low temperatures (3⚬-5⚬ C.). The vegetative nuclei contain a granular network which is stainable by the Feulgen technique. Certain of the ascostroma primordial cells become sexually active and act as ascogonia. The nuclei of these cells show a single large Feulgen-positive granule. These nuclei increase in number and size, and the ascogonial cell puts out branched ascogenous hyphae, the tips of which swell to form the ascus initials. No sexually differentiated gametic branches nor any cell or nuclear fusion is seen at this stage. Nuclear fusion occurs between the two nuclei always found in the ascus initials. Spore formation follows the usual course found in the ascomycetes. The cells of the mature spore are multinucleate.