. Sexual reproduction and the organization of the nucleus in certain mildews. beginning to swell. Fig. 12.—Oogonium still uninucleated. Wall of antheridium swollen and show-ing strong affinitj- for orange stain. Early stage of perithecial walls. Fia 13.—Egg-nucleus has di\ided. Fig. 14.—.Vscogonium binucleated. Stalk-cell of antheridiiam has grown outinto a h>T3hal branch, which curves over the antheridium and is a part of theperithecial walL Fig. 15 a, b.—Two sections of the young ascocarp. Antiieridium with thick walland dense content Fig. 16.—Slightly older; perithecial wall becoming two
. Sexual reproduction and the organization of the nucleus in certain mildews. beginning to swell. Fig. 12.—Oogonium still uninucleated. Wall of antheridium swollen and show-ing strong affinitj- for orange stain. Early stage of perithecial walls. Fia 13.—Egg-nucleus has di\ided. Fig. 14.—.Vscogonium binucleated. Stalk-cell of antheridiiam has grown outinto a h>T3hal branch, which curves over the antheridium and is a part of theperithecial walL Fig. 15 a, b.—Two sections of the young ascocarp. Antiieridium with thick walland dense content Fig. 16.—Slightly older; perithecial wall becoming two-layered. Fig. 17a,b.—Yoimg ascocarp in two sections; uninucleated cell cut off fromthe end of multinucleated ascogonium; perithecial hj-pha is shown arising fromstalk of antheridium. Fig. i8a,fc.—Somewhat older; end cell of ascogoniimi separated from theantheridium by crowding in of the perithecial hj-phae. Fig. 19.—-\scogonium with three cells, the next to the last binucleated, theothers uninucleated. The whole ascocarp is perhaps dwarfed in this case. ^^. 94 EXPLAXATION OF FIGURES IN PLATES. Plate II.—PHYtLAcriNiA corylea. Fig 20 a, fc.—Ascogonium with four cells; the apical cell uninucleated and nar-rowed above by pressure of surrounding hyphae. Penultimate cell of basal cell in next section. Fig. 21 a,b.—Ascogonium four-celled; basal cell with two 22.—Ascogonium with five cells; penultimate cell budding out in asco-genous hyphs; nuclei of second and third cells in another section. Fig. 23—Perithecial cells with resting nuclei and a metaphase stage of nucleardivision; nucleolus near one pole of spindle. Fig. 2+—Resting nucleus from mycelial h>T)ha with central body connected withchromatin. Fig. 25 a, 6.—Ascogonium with five cells; penultimate cell budding out in asco-genous h\phK; apical cell still connected to thick-walled antheridium. Fig. 26.—Median section of older ascocarp, showing sections of ascogenou
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