ASCOSPORES 



23 



The paired nuclei come to lie side by side in the terminal cell (Fig. 

 14a) which bends to form a crozier (Fig. 14a). Each nucleus divides 

 (Fig. 146) and two septa are formed, one isolating a single nucleus 

 in the crozier, now the terminal cell, and one nucleus of opposite sex 

 in the antepenultimate cell (Fig. 14c). The penultimate cell still 

 has two nuclei, one of each sex. The crozier cell and the antepenulti- 

 mate cell now anastamose and simultaneously the penultimate cell 

 either forms another crozier (Fig. 14(i) or else the nuclei fuse (Fig. 



Fig. 15. Apothecia of Peziza sylvestris. From F. J. Seaver, The North American 



Cup-Fungi, 1928. 



14e). If the former happens we may have several croziers being 

 formed at the same time, for the cell formed by the union of crozier 

 and antepenultimate cells, as well as the penultimate cell, now the 

 new terminal cell, may form a crozier, and thus we may have a com- 

 plicated system of ascogenous hyphae. Eventually, however, the 

 nuclei fuse in the penultimate cells (Fig. 14e) of the ascogenous 

 hyphae. This diploid nucleus undergoes reduction division, and each 

 cell divides twice again (Fig. 14/) and the eight haploid asco- 

 spores are produced in this cell which becomes enlarged to form an 

 ascus. While the ascogenous hyphae are thus proliferating, the 

 mononucleate or multinucleate mycelium arising from the cells which 

 bore the oogonium and antheridium may form a complicated net- 

 work of mycelium to cover the ascogenous hyphae. This becomes 

 the ascocarp. There are many modifications of the above process. 

 By far the greatest number of the species of Ascomycetes have 

 eight ascospores per ascus. Whereas in the lower Ascomycetes the 

 ascospores may be formed on any part of the mycelium, in the higher 



