. Chestnut blight. Chestnut blight; Chestnut. S78 Bulletin 347 the winter months. Fresh spore horns are not seen during the winter, but this may be due to the fact that they are produced at such a slow rate that they are washed away before their size makes them noticeable. Development of perithecium.— The beginning of the perithedai stage is accompanied by a marked increase in the size of the stroma, which now pushes off more of the cork layer and not only fills up the enlarged rent but also grows out over the torn edges so that they are included in it (Fig. 8s, page 558). The stroma takes on
. Chestnut blight. Chestnut blight; Chestnut. S78 Bulletin 347 the winter months. Fresh spore horns are not seen during the winter, but this may be due to the fact that they are produced at such a slow rate that they are washed away before their size makes them noticeable. Development of perithecium.— The beginning of the perithedai stage is accompanied by a marked increase in the size of the stroma, which now pushes off more of the cork layer and not only fills up the enlarged rent but also grows out over the torn edges so that they are included in it (Fig. 8s, page 558). The stroma takes on an erumpent, superfidaL appear- ance (Plate XXXVII). This change has been observed within eight weeks after inoculation; on trees inoculated in June the stromata have been found in Fig. 93.— Stages in the development of the carpogonium. The larger, heavily shaded cells at the center are the ascogonial cells, with the cells of the enveloping hyphx about them. The last figure shows the continuation of the ascogonium into the trichogyne. All figures are drawn to the same scale The primordia — beginnings of the perithecia — arise in the base of the stroma or even among the outermost cells of the host. Each prim- ordium consists of two to five large, prominent cells arranged in a circle or a spiral (Fig. 93), closely invested by a sheath of large hyphse. The central prominent cells form the ascogonitim, and the investing hyphas win here be called the envelope. The ascogonium, which is an enlarged single hypha, is continued up to the surface of the stroma as a prominent thread, the trichogyne. There may be as many as a hundred primordia in a single stroma, but only about one fourth of them ever reach maturity; the others degenerate at various stages of development. The ascogonial cells are dongated-oval, slightly curved so as to fit the segment of the spiral, deeply constricted at the septa, and only loosely. Please note that these images are extracted from scanned p
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