568 COMPARATIVE MORPHOLOGY OF FUNGI 



binucleate and, occasionally secondarily, a multinucleate mycelium (Fig. 

 379, 2). At the germination of the urediniospores there is no change in 

 host. On this binucleate mycelium there may arise uredinia with ure- 

 diniospores which develop a new mycelium, which again forms uredinia, 

 so that several generations of uredinia with uredinial mycelium follow 

 one another within a single growing period. In the binucleate mycelium, 

 the urediniospores play the same role of rapid propagation as the conidia 

 on the haploid mycelium. 



After a definite length of time telia (sori of teliospores) appears on 

 the binucleate mycelium. The exact moment of their appearance 

 depends upon the condition of nutrition of the host and generally cor- 

 responds with the end of the growing season; it can be retarded or 

 hastened by the environment (Iwanoff, 1907;Morgenthaler, 1910;Gassner, 

 1916). The teliospores are the homologs of the probasidia and sclero- 

 basidia of the Auriculariales: the dicaryon fuses in them to a single 

 diploid nucleus which gradually prepares for meiosis. In contrast to the 

 urediniospores, which arise during the diplophase, the teliospores terminate 



this diplophase. 



In addition to these normal forms, in which the telia arise on the 

 binucleate mycelium, telia (in forms which lack the aecia and uredinia) 

 may be formed directly on the uninucleate mycelium. In this respect 

 five groups may be distinguished. In the first group, to which belong 

 Uromyces scutellatus, U. laevis, Puccinia Fergussoni, P. Rossiana, Chryso- 

 myxa Abietis (Kursanov, 1922), Uromyces alpestris (Tranzschel, 1910) 

 and Galloway a pinicola (B. O. Dodge, 1925), the telia closely resemble 

 the aecia; thus in U. alpestris they are formed in the interior of aecidia 

 which do not open as such, and in U. scutellatus on Euphorbia the remains 

 of the aecidial fundaments are indicated by peridial cells in the young 

 telia. In their development, they correspond to aecia, e.g., those of the 

 type of Puccinia Violae: the thick hyphal knot is differentiated into an 

 upper sterile and lower fertile zone. Between two palisade cells or 

 between two vegetative cells or between a palisade cell and a vegetative 

 cell, plasmogamy occurs and the fusion cells develop to short, branched 

 hyphae on whose ends are formed the teliospores. Similarly, the telia 

 of Puccina Anemones {P. fusca) on Anemone nemorosa develop exactly 

 as the aecia of Ochropsora Ariae on the same host (Lindfors, 1924). 



In a second group including, among others, Puccinia Malvacearum 

 (Mme. Moreau, 1914; Werth and Ludwigs, 1912), P. transformans (Olive, 

 1908), P. Buxi (Mme. Moreau, 1914) and probably also P. Liliacearum 

 (Maire, 1899), differentiation occurs as in a caeoma: on the top of the 

 hyphal knot there are formed palisade cells which copulate with each 

 other or with hyphal cells. 



In a third group, e.g., Uromyces Ficariae (in which the uredinium is 

 acking) there is, as in Endophyllum Sempervivi, no definite palisade forma- 



