[Vol. 2 

 342 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



ber of chromosomes in all three divisions, in some species 4 

 or 5 (Hydnobolites), in others 8 (Neotiella). 



More recently Claussen ('12) after a very thorough study 

 of Pyronema confluens finds the same number of chromosomes 

 (about 12) in all three divisions. The first division is hetero- 

 typic accompanied by synapsis, diakinesis and a splitting of 

 the chromosomes. The second is homootypic, while the third 

 is typic. Faull ('12) in a recent study on Laboulhenia also 

 finds that the two first divisions in the ascus agree with the 

 usual phenomena accompanying reduction in spore mother 

 cells, the first being heterotypic, while the second follows 

 ''very swiftly on the heels of the first." He concludes that 

 "probably the only nuclear fusion in the life cycle is that in 

 the ascus," and that conjugate divisions of nuclei are an im- 

 portant phase in the sexual phenomena of the Ascomycetes. 



The evidence from recent investigations, therefore, supports 

 more and more the interpretation of nuclear fusion in the 

 ascus as a process of exactly the same significance as the 

 nuclear fusion in the basidium of the Basidiomycetes, and in 

 the teleutospore of the Uredinales, i. e., it is the fusion of a 

 pair of nuclei of a longer or shorter history of conjugate divi- 

 sions from a pair of ancestral nuclei of more or less remote 

 association. This association of nuclei arises in a variety of 

 ways and at different periods in the ontogeny just as it does 

 in the Basidiomycetes (Maire, '02; Ruhland, '01; Harper, '02; 

 Nichols, S. P., '04; Kniep, '13), and Uredinales (Sappin- 

 Trouffy, '96; Maire, '99, '01; Blackman, '04; Christman, '05, 

 '07; Blackman and Fraser, '06; Olive, '08; Hoffmann, '12; 

 Werth und Ludwigs, '12). The association is accomplished 

 in some cases through the copulation of two gametangia 

 {Pyronema, Monascus, Gymnoascaceae, and the Erysipheae). 

 Such an association represents nearly, if not quite exactly, 

 the true type of sexuality. The other methods of association 

 represent a variety of modified types of sexuality (see Note i) 

 where the archicarp is present and the antheridium absent, or 

 functionless, or where the archicarp is absent and vegetative 

 cells, either with or without the migration into them of nuclei 



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