1915] 



ATKINSON PHYLOGENY IN THE ASCOMYCETES 



339 



Others maintam with equal assurance that there is no fusion 

 of the sexual nuclei in the archicarp. There is merely an asso- 

 ciation of sex nuclei. 



(1). In forms with a func- 

 tional antheridium and archicarp 

 may be mentioned Monascus'^ 

 (Schikorra, '09) and Pyro- 

 nema confluens (Claussen, '07, 

 '12). 



(2). In forms where the an- 

 theridium is absent or function- 

 less may be mentioned Pyronema 

 confluens (Brown, W. H., '09, an- 

 theridium functionless), Lachnea 

 scutellata (Brown, W. H., '11, 

 antheridium absent). In both of 

 these examples, cases of division 

 of the nuclei in the ascogonium 

 were observed which might be 

 mistaken for fusion. Since no 

 divisions of nuclei in the as- 

 cogonium have been described by 

 authors in the forms where they 

 believe sexual fusions of nuclei 

 to take place, W. H. Brown ('11) 

 suggests that they may have had 

 before them division stages. In 



Ascophanus carneus and Ascobolus immersus the anther- 

 idium is absent, but association of the nuclei in several of the 

 multinucleate ascogonial cells occurs after pore formation in 

 the walls. Most of these nuclei become paired and remain 

 paired as they migrate in the ascogenous hyphae to the ascus 

 hooks, where conjugate division takes place. The only fusion 

 of nuclei is that in the ascus, except in badly fixed prepara- 

 tions or in degenerating nuclei in the ascogonium (Ramlow, 

 '14). In Leotia (Brown, W. H., '10) the ascogenous hyphae 



^ Barker ('03) ascribed his failure to find a fusion of nuclei in the ascogonium 

 of Monascus to the absence of proper stages in his material. 



Ascog. 



Fig. 9. Pyronema confluens: A, 

 B, and C, conjugate division of 

 nuclear pairs in the ascogenous 

 hyphae; D, conjugate division in 

 ascus hook; E, tips of branched 

 ascogenous hyphae with ascus 

 hooks, young asci, and beginning of 

 conjugation of the ultimate and 

 antepenult cells of the ascus hooks ; 

 P, completed conjugation of the 

 ultimate and antepenult cells of 

 the hook and association of their 

 nuclei as a pair. Ascog, ascogo- 

 nium; asc. h, ascogenous hyphae 

 with paired "sexual" nuclei. — After 

 Claussen. 



