ASCOMYCETES 



123 



(Pig. 11, n) . Subsequently it divides by septa so that in the vicinity of the 

 ascogonium the cells contain 2-8 dicaryons and farther away only one (Fig. 



11, 4). A cell with only one dicaryon puts forth a lateral process whereby the 

 nuclei are rather far separated (Fig. 11, 6) ; shortly the process bends around 

 into a crozier, and the nuclei begin to divide conjugately (Fig. 12, 1). The 

 spindles lie approximately parallel to each other. After the division, the crozier 

 is ab jointed from both the tip and stipe cells which contain one nucleus each 

 (Fig. 12, 2). In the simplest case the nuclei of the crozier fuse to a diploid 

 nucleus, the primary ascus nucleus, and the crozier develops an ascus (Fig. 



12. 3). 



In another type, the crozier develops a new crozier which in turn may 

 develop still another. In any case it is only the terminal crozier that develops 





mi 



m 



wmm 



Fig. 12. — Pyronema confluens. 1, Older ascogenous hypha with a new ascogenous hypha 

 budding out to form croziers, the tip cell uninucleate. 3, A crozier, showing fusion in the 

 ascus cell. S, Prophase in the two nuclei of a crozier, each showing twelve chromosomes. 

 4, First mitotic telophase in the ascus with twelve whole chromosomes going to each pole. 5, 

 Metaphase of the second division in the ascus, showing six chromosomes. 6, Third division 

 in the ascus ; the lower nuclei are in the late metaphase, the next shows the anaphase, and 

 that nearest the apex an ea.rly telophase in which six chromosomes can be counted at the 

 pole. 7, Mycospliaerelln Fragariae, a tvpical peritheciuni. 8, Ascospores. (/ and 2 Xl,230 : 

 S-6 XI, 760; 7 X360 ; S X800.) (After Gwynne Vaughan & Williamson, 1931 and Klebahn 

 1918.) 



an ascus. In a third type, the dicaryon of the crozier divides without form- 

 ing any new crozier. The original crozier develops a branch which later may 

 form a new crozier whereon an scus may arise directly; or caryogamy may 

 again be retarded with the result that a tuft of croziers is formed. Occa- 

 sionally the stipe and tip of the crozier fuse, the stipe nucleus generally 

 migrating into the tip cell. This proceeds to develop a binucleate branch 

 which gradually forms a crozier that may develop an ascus by fusion of its 

 nuclei or repeat crozier formation. 



