Stroma and Formation of Perithecia in Hypoxylon

Abstract

1. The stroma is differentiated into four regions, and in one of these further zonation is evident. 2. The firm structure of the stroma is gained by various mechanical devices for support, such as tubular extensions from cells, branching and intertwining of hyphae, and special articulation surfaces. 3. The hyphae are differentiated into three types from the time of their emergence from the substratum: those that form the major part of the stroma, those that form the perithecia and Woronin hyphae, and those that form the superficial layers and probably the conidiophores. 4. The cells of the hyphae are originally binucleate, but may become multinucleate. 5. The formation of the perithecia is initiated by the massing of the hyphae into a circular knot, within the center of which the Woronin hyphae differentiate. 6. The ascogonia develop from the cells of the Woronin hyphae by rounding out, partially separating from each other, and increasing in size. 7. The ascogonia do not drop to the bottom of the perithecium in the older stages, but come to lie comparatively closer to the bottom by an expansion of the perithecial wall toward the periphery of the stroma. 8. The nuclear program within the ascogonia is one of few divisions and great increase in size, up to the stage where the ascogonia are well rounded out, and then of rapid division without the maintenance of size. 9. The ascogonium buds out protuberances that are the beginnings of the ascogenous hyphae