. Comparative morphology of Fungi. Fungi. ASCOMYCETES 135 each other by a gelatinous appendage. The rest of the ascus collapses, withdraws and makes place for the next. The height of projection of the ascospores occasionally attains a relatively enormous value if one considers that the perithecia are only about half a millimeter high in the middle. Thus in Podospora fimiseda, it reaches 15 cm. and in P. curvi- colla, as high as 45 cm. (Weimer, 1920). In other forms, as Leptosphaeria acuta (Hodgetts, 1917), Pleospora her- barum (Atanasoff, 1919) and P. scirpi- cola (Pringsheim, 1858), this disc
. Comparative morphology of Fungi. Fungi. ASCOMYCETES 135 each other by a gelatinous appendage. The rest of the ascus collapses, withdraws and makes place for the next. The height of projection of the ascospores occasionally attains a relatively enormous value if one considers that the perithecia are only about half a millimeter high in the middle. Thus in Podospora fimiseda, it reaches 15 cm. and in P. curvi- colla, as high as 45 cm. (Weimer, 1920). In other forms, as Leptosphaeria acuta (Hodgetts, 1917), Pleospora her- barum (Atanasoff, 1919) and P. scirpi- cola (Pringsheim, 1858), this discharge is favored by an anatomical differentia- tion of the ascus wall. This consists of two layers which are only recognizable at the moment of spore liberation, a rigid inelastic cuticular outer layer which does not swell in water, and a thicker gelatinous inner which absorbs water and swells. The paraphyses also swell in damp weather. By the pres- sure of the swollen inner layer, the outer ruptures at the tip, the inner together with the ascospores pushes out, tears open laterally with a jerk at the point of emergence or at the top and dis- charges the ascospores. In still other forms, as in Endothia parasitica and in many Gnomoniaceae, the length of the perithecial neck does not permit the asci, as in Podospora, to reach the opening and there to eject their spores. Hence they break loose from their point of formation and closely press together, more or less parallel, with the tip, directed toward the entrance canal and fill up the interior of the peri- thecium. Hereupon they are gradually pressed out through the canal by the periphyses. On the drying of the peri- thecial neck, the asci are pressed together until they rupture under the lateral pressure and discharge their spores. Thus the mechanism of discharge here rests in the perithecial opening; if this is cut off, at least in Endothia parasitica, spore discharge ceases (Heald and Walton, 1914). The apothecium, the second
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