. The fungi which cause plant disease . Plant diseases; Fungi. THE FUNGI WHICH CAUSE PLAXT DISEASE 331 In all of the rusts so far investigated that have an aecium or primary uredinium there is in the aecio-mycehum or the primary uredinio-mycelimn a fusion of uninucleated cells, gametes. This cellular fusion is not, however, followed by a nuclear fusion until after long delay; but the two nuclei remain in the fusion cell and when this cell divides both nuclei divide mitotically and simul- taneously but still independently of each other (conjugate division). This process continues through the ae
. The fungi which cause plant disease . Plant diseases; Fungi. THE FUNGI WHICH CAUSE PLAXT DISEASE 331 In all of the rusts so far investigated that have an aecium or primary uredinium there is in the aecio-mycehum or the primary uredinio-mycelimn a fusion of uninucleated cells, gametes. This cellular fusion is not, however, followed by a nuclear fusion until after long delay; but the two nuclei remain in the fusion cell and when this cell divides both nuclei divide mitotically and simul- taneously but still independently of each other (conjugate division). This process continues through the aecial sporophores, or uredinial sporophores, and in the production of the spores, with the result. J ^3. Cm., rf-% t Fig. 244.—Showing Ronjugate nuclei and degenerating cells in conidiospore chain of .£cidium. After Sappin-TrouSfy. Fio. 245.—Gymnospo- rangium, clavariiB- forme, mitosis of a nucleus in the promy- eelium. After Black- FiG. 246. — Conjugate nuclear division in Gymnosporangium clavarioeforme show- ing four chromatin masses. After Blackmau. that the cells of all of these are binucleate. The conjugate divi- sion continues further through the uredinia and until teUospore formation occurs, the whole intervening series of cells being binu- cleate. Prior to the formation of the promycelium and in the teliospore the nuclei unite, reducing the cells again to an uninu- cleate condition. In rusts which have only teliospores the binucleate condition begins somewhere in the mycelium from which the teliospores arise. It is generally held that the cellular fusion is a sexual act with long delayed fusion of the sexual nuclei: and consequently that the uninucleate phase is the gametophj^te; that the be-. 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 Stevens, Frank Lincoln, 1871-1934. New York : Macmilla
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectfungi, bookyear1913
