4Q ASCOMYCETES [ch. 



contents of the antheridium enter the oogonium which, as a result of this 

 association, gives rise in nearly every case, with or without preliminary 

 septation, to a number of filaments, the ascogenous hyphae, from the tips 

 of which asci grow out. The ascogenous hyphae thus constitute the sporo- 

 phyte while the vegetative mycelium, on which the sexual organs are borne, 

 is the gametophyte. The gametophyte gives rise to the peridium and the 

 paraphyses, and on it the various accessory spores are produced. 



Early Investigators. The history of the minute study of the Asco- 

 mycetes may be said to have begun in 1791 when Builliard, in his Histoire 

 des Champignons de France, described the asci as female organs, and sug- 

 gested that their fertilization was accomplished by some substance emanating 

 from the paraphyses. 



In and after 1863 the classical researches of de Bary and his pupils 

 established the existence of male and female organs at the beginning of 

 ascocarp formation in a number of species. They brought forward evidence 

 of the occurrence of fertilization in some cases and in others of development 

 without an antheridium (parthenogenesis) or without either male or female 

 organs (apogamy), they showed that the paraphyses and sheath of the 

 ascocarp arise from the vegetative mycelium and the ascogenous hyphae 

 from the female branch. The conclusions reached by de Ban- are summed 

 up in the fifth chapter of his book on the Comparative Morphology and 

 Biology of the Fungi, Mycetozoa and Bacteria, first published in 1884, and 

 they have been largely confirmed by subsequent investigation. 



In 1 88 1 Eidam observed the formation of the ascus in the very simple 

 genus Eremascus, where it arises from two separate filaments which become 

 intertwined and fuse at their tips. 



De Ban's views were extensively criticized, especially by van Tieghem 

 and Brefeld, who both denied the occurrence of sexuality in the group. 

 These and other writers sought to explain the antheridial filament as part 

 of the sheath, and the archicarp as a precocious ascogenous hypha, or, in 

 certain lichens, as a boring or a respiratory organ. Brefeld was the author 

 of a scheme of classification, which, if too rigid to endure the test of sub- 

 sequent work, was at least exceedingly convenient. With it, and especially 

 in the text book of his disciple von Tavel (1892), his view that the higher 

 fungi lacked sexuality was widely disseminated. 



Cytology. In the meantime considerable advances were being made in 

 the stud\- of cytology and of the cytological methods necessary for the exami- 

 nation of minute forms. De Bary, in 1863, had recognized the presence of a 

 single or definitive nucleus in the immature ascus of Pyronema cottfluens and 

 some other species, and the successive appearance as development proceeded 

 of two, four, and eight nuclei. He found that the eight nuclei lay at more or 

 less equal distances apart, and that each became surrounded by a mass of 



