. Fungi, ascomycetes, ustilaginales, uredinales. Fungi. 206 PROTOBASIDIOMYCETES [CH. in kind from the normal process. In Pinus sylvestris^ the male and female nuclei lie side by side but do not fuse till their chromosomes become mingled on the first spindle of the embryo; in many of the protozoa and in some other animals a series of conjugate divisions may precede the combination of the paternal and maternal chromosomes in a single Fig. i8i. Puccinia Potiophylli S.; fertile cell of teleutosorus giving risetoteleutospores; after Christ- Fig. iS'Z. Phraamidium violaceum Went.; a. tele
. Fungi, ascomycetes, ustilaginales, uredinales. Fungi. 206 PROTOBASIDIOMYCETES [CH. in kind from the normal process. In Pinus sylvestris^ the male and female nuclei lie side by side but do not fuse till their chromosomes become mingled on the first spindle of the embryo; in many of the protozoa and in some other animals a series of conjugate divisions may precede the combination of the paternal and maternal chromosomes in a single Fig. i8i. Puccinia Potiophylli S.; fertile cell of teleutosorus giving risetoteleutospores; after Christ- Fig. iS'Z. Phraamidium violaceum Went.; a. teleuto- spores, X 1080; /;. fusion of nuclei in teleutospore, X 1520; after Blackman. It may be hazarded that in the Uredinales the similarity of the physio- logical history of the nuclei before they become associated is responsible for a minimum of attraction between them, so that there is no sufficiently strong impulse towards fusion till meiosis is about to take place; being, however, in the same cell, they have no opportunity of dissolving partnership and the influences which bring about meiosis affect both alike. A considerable similarity exists in the arrangement of the different groups of sporogenous cells. The uredo- and teleutosori are clearly com- parable, both are of indefinite extent, with or without a border of paraphyses, and both consist of groups of rectangular basal cells from which the spore mother-cells arise in horizontal series and divide to produce the simple or compound spore and the stalk-cell. Sometimes, however, the uredospores are borne in vertical series, one below the other, and the sister-cells of the spore form short, intercalary cells instead of stalk cells (fig. 183). This arrangement and that of the so-called primary uredospores link the uredosorus to the aecidium, suggesting the homology of the stalk and inter- calary cells. In the simplest aecidia, those of the caeoma type, we have a ^ Blackman, V. H., 1898, Phil. Trans. B. cxc, p. 395. Please n
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