. Fungi, ascomycetes, ustilaginales, uredinales. Fungi. 192 HEMIBASIDIOMYCETES [CH. Basidiospores are budded off in abundance from all three cells, and in turn give rise to conidia. In the meantime the basidium has separated from its parent brand-spore, and the spore, after nuclear division, may produce another basidium, and others in succession at the same spot, so that free basidia accumulate in the culture. If cultures in nutrient solution are allowed to starve, association now takes place between basidial cells, basidiospores or conidia by means of conjugating tubes (fig. 158 (5). The pair
. Fungi, ascomycetes, ustilaginales, uredinales. Fungi. 192 HEMIBASIDIOMYCETES [CH. Basidiospores are budded off in abundance from all three cells, and in turn give rise to conidia. In the meantime the basidium has separated from its parent brand-spore, and the spore, after nuclear division, may produce another basidium, and others in succession at the same spot, so that free basidia accumulate in the culture. If cultures in nutrient solution are allowed to starve, association now takes place between basidial cells, basidiospores or conidia by means of conjugating tubes (fig. 158 (5). The paired cells increase markedly in volume,, but no interchange of cytoplasm takes place and the nuclei remain in their respective cells without visible change. Harper observed that when fresh beerwort was supplied to his cultures at this stage the produc- tion of conidia began again. They are produced from one or both of the con- jugating cells, but only a single nucleus is concerned in the development of each conidium, the other remains quiescent and the conidia are uninucleate. In a host plant, the name of which is not recorded, Werth and Ludwig failed to find binucleate elements, the youngest cells in which they could iden- tify the nuclei being uninucleate (fig. IS9«). They infer that in this species nuclear association fails to take place, and no binucleate stage exists. This hypothesis accords well with Harper's observations on the saprophytic phase which he studied in material grown on Lychnis alba. On the other hand, a binucleate stage was identified by him in the sporogenous cells of U. an- therarum on Saponaria, and by Dangeard on Lychnis dioica. These facts suggest the possibility of two or more varieties of U. antherarum on different hosts and differing in their cytological behaviour; the forms studied by Dangeard and Harper point to a condition comparable to that of U. Maydis, while Werth and Ludwig's observations indicate the possibility of a truly apogamous strain. A
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectfungi, bookyear1922
