Fungous diseases of plants . ssesin the Uredinales. It had been known since the studies of Sappin-Trouffy and Dangeard that the binucleate condition of the teleuto-spore and of the mycelium preceding it leads finally to a fusion ofthese two nuclei preceding the development of the recent studies have been directed primarily toward a knowl-edge of the origin of this binucleate condition. Blackman in someextensive studies of a caeoma stage, in particular, demonstrated whathe believed to be a fusion phenomenon in the following manner :During the early development of this stage nume
Fungous diseases of plants . ssesin the Uredinales. It had been known since the studies of Sappin-Trouffy and Dangeard that the binucleate condition of the teleuto-spore and of the mycelium preceding it leads finally to a fusion ofthese two nuclei preceding the development of the recent studies have been directed primarily toward a knowl-edge of the origin of this binucleate condition. Blackman in someextensive studies of a caeoma stage, in particular, demonstrated whathe believed to be a fusion phenomenon in the following manner :During the early development of this stage numerous gameticbranches arise. These come in contact in pairs, the older and 394 raiNGOUS DISEASES OF PLANTS larger branch cutting off an apical cell. The smaller gamete intime loses its nucleus by migration through a pore into the largergamete, and the cells thus provided with two nuclei become eachproperly the basal cell of one of the chains of spores which arisein this type, corresponding to the aecidium, each spore of which. Fig. 194. PiiKAGMiDiuM sPEciosuM: Df-velopment of /Ecidiospores(After Christman) (7, progametes ; b, gamete and sterile cell; c, after gametic fusion and nucleardivision ; d and c, spore production possesses paired nuclei. He would also homologize the apical cellof the larger gamete with the trichogyne of certain lower plants, andwould assume that in the phylogeny of these plants the spermatiawere functionally in connection with this Organ. The work ofChristman and Olive on this and other rust fungi in part confirmBlackmans results. They are also able to identify the gametes, butthe communication between these two adjacent cells is generally, PROTOBASIDIOMYCETES 395 however, effected by a dissolution of the upper portion of the cellwalls in contact, thus securing a union of two cells. From theseunited cells, with two nuclei, as a basal structure arise the chain ofspores as before. The evidence offered seems to thoroughly explainthe origin of the binucleate
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