Ascocarp Development in Two Homothallic Neurosporas

Abstract

Perithecia of Neurospora terricola and N. dodgei are initiated by the formation of a coiled archicarp, the terminal portion of which is soon differentiated as an ascogonium consisting of several cells. Sterile hyphae which early envelop the female organ give rise to the ascocarp wall. No trichogynes were identified. When the protoperithecium of N. terricola has reached a diameter of approximately 100 /u and that of N. dodgei about 160 u, primary ascogenous hyphae start to develop from the ascogonium. Immediately above these a centrum cavity appears into which paraphyses quickly grow. Asci do not appear until the centrum has attained nearly its maximum size and an ostiolar canal has been formed. As the asci develop, the paraphyses disintegrate. It is concluded that the perithecial centrum is of the "Xylariatype," as defined by Luttrell, and that Neurospora should therefore be placed in the Xylariales in the Luttrell scheme of classification. In many morphological and cytological features, N. terricola and N. dodgei resemble closely not only other species of Neurospora previously studied but also other members of the Sordariaceae (sensu Moreau), particularly members of the genera Gelasinospora, Sordaria, and Pleurage. Noteworthy cytological features encountered were: multinucleate ascogonial cells; ascospores initially uninucleate but becoming binucleate prior to maturation; in N. terricola beaked nuclei bearing prominent appendages at the 4-nucleate stage of ascus development; and a haploid chromosome number of 7 in N. terricola.