. Chestnut blight. Chestnut blight; Chestnut. 58o Bulletin 347. has become completely filled with maturing asci and the perithecium is now ready to discharge its spores. Time of development of perithecia.— On cankers produced by inoculation during spring and summer, mature perithecia are de- veloped in early autxmm. It is evident, however, that this is not the only season at which they may be produced, be- cause there is no time of the year at which they cannot be fovmd in abundance, ready to eject spores if the proper conditions of moisture and temperature are supplied. Ejection of ascospores
. Chestnut blight. Chestnut blight; Chestnut. 58o Bulletin 347. has become completely filled with maturing asci and the perithecium is now ready to discharge its spores. Time of development of perithecia.— On cankers produced by inoculation during spring and summer, mature perithecia are de- veloped in early autxmm. It is evident, however, that this is not the only season at which they may be produced, be- cause there is no time of the year at which they cannot be fovmd in abundance, ready to eject spores if the proper conditions of moisture and temperature are supplied. Ejection of ascospores One of the writers of this bulletin (Rankin, 1912 a) dis- covered that during rain periods the ascospores are ejected with some force into the air from the. ostioles of the perithecia. The asci, which usually fill the peri- thecium, are pushed up through the neck when abtm- This expulsion of the asci is. Fig. 95.— Cross section of the young perithecium before the differentiation of the wall and the core cells, showing at the center the shriveled remains of an ascogonial cell and at the top the begin- ning of the neck dant free water is added to the stroma, largely due to the swelling pressure of the asci. A dry ascus with its spores (Fig. 89, b, page 562) occupies oiHy about one half the space occupied by an ascus after water is added (Fig. 89, c and d). Prepared sections of perithecia fixed during the process of ejection of spores show that the spores remain in the asci almost to the tip of the neck. Since the asci themselves are never ejected into the air, it follows that they must burst and liberate the spores when they arrive at the surface of the film of water. The ejection may be observed with a hand lens. The only visible phenomenon is the sudden and regular breaking of the film over the ostiole. This gives for the moment the impression of a point of light. The entire contents of the ascus are ejected at once into the air. Rankin (1914) has drawn the following concl
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Keywords: ., bookcollectionbiodiversity, bookleafn, booksubjectchestnutblight
