SUMMARYPerithecia ofNeurospora terricolaandN. dodgeiare 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 ofN. terricolahas reached a diameter of approximately 100μand that ofN. dodgeiabout 160μ, 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 thatNeurosporashould therefore be placed in the Xylariales in the Luttrell scheme of classification.In many morphological and cytological features,N. terricolaandN. dodgeiresemble closely not only other species ofNeurosporapreviously studied but also other members of the Sordariaceae (sensuMoreau), particularly members of the generaGelasinospora, Sordaria, andPleurage.Noteworthy cytological features encountered were: multinucleate ascogonial cells; ascospores initially uninucleate but becoming binucleate prior to maturation; inN. terricolabeaked nuclei bearing prominent appendages at the 4-nucleate stage of ascus development; and a haploid chromosome number of 7 inN. terricola.