. Fungi, ascomycetes, ustilaginales, uredinales. Fungi. VIII] UREDINALES 20[. Fig. 172. Phragmldium speciositm Fr.; a. fertile and sterile cells; b. fusion of two fertile cells; after Christman. cells below them (Fromme '14), or each may receive a second nucleus by migration from a neighbouring vegetative cell (fig. 173). In each case they now constitute the basal cells of the rows of spores and they proceed at once to cut off aecidiospoi'e mother- cells, each of which in turn divides to separate a small intercalary cell below from the aecidiospore above. Exceptionally binucle- ate cells may b
. Fungi, ascomycetes, ustilaginales, uredinales. Fungi. VIII] UREDINALES 20[. Fig. 172. Phragmldium speciositm Fr.; a. fertile and sterile cells; b. fusion of two fertile cells; after Christman. cells below them (Fromme '14), or each may receive a second nucleus by migration from a neighbouring vegetative cell (fig. 173). In each case they now constitute the basal cells of the rows of spores and they proceed at once to cut off aecidiospoi'e mother- cells, each of which in turn divides to separate a small intercalary cell below from the aecidiospore above. Exceptionally binucle- ate cells may be observed before the fertile layer is differentiated. InPuccmia Poarnm nuclear migrations sometimes take place be- tween the vegetative cells at the base of the very young aecidium. These cells may grow up, either at once or after division, to form fertile cells. The aecidiospores, then, are the products of a sexual process by means of which two nuclei become associated within the limits of a single protoplasmic mass, form- ing the dikaryon or synkaryon of Maire. The nuclei thus brought together do not fuse, but undergo simultaneous division (fig. 174), so that a daughter nucleus from each passes into every new cell. Conjugate division is continued when the aecidiospore germinates and a mycelium of binucleate cells is produced. The sporophyte of the rusts is thus normally inaugurated in the fertile cells of the aecidium. It is not unusual to find spores and vegetative cells which contain three or more nuclei; in these, as in the binucleate cells, and, indeed, in multinucleate cells of many different groups of plants, conjugate. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Gwynne-Vaughan, Helen Charlotte Isabella (Fraser) Dame, 1879-. Cambridge [Eng] University Press
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectfungi, bookyear1922
