[VOL. 2 

 338 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



by an antheridium (Harper in Sphaerotheca castagnei,^ '95% 

 '96 ; Erysiphe, '96 ; Pyronema confluens, '00 ; Phyll actinia, '05 ; 

 Blackman and Fraser in Sphaerotheca, '05 ; Claussen in Bou- 

 diera [=Ascodesmis'\, '05) ; or (2) in the archicarp where the 

 antheridium is functionless or absent (Blackman and Fraser, 

 '06, in Eumaria granulata; Fraser, '07, in Lachnea stercorea) . 

 In. Aspergillus herbariorum Miss Fraser (07, p. 420) finds that 

 the antheridium often degenerates and did not observe disap- 

 pearance of the intervening wall when fusion with the tricho- 

 gyne took place. She nowhere describes or figures fusion in 

 pairs of the ascogonial nuclei. She merely assumes it, for, in 

 the summary ('07, p. 428) she says: ''It seems probable that 

 normal fertilization occurs in some cases, and that in others it 

 is replaced by a fusion of ascogonial nuclei in pairs ' ' ; Wels- 

 ford ( '07) in Ascoholus furfuraceus; Dale ( '09) in Aspergillus 

 repens; Cutting ('09) in Ascophanus carneus believe in the 

 fusion of archicarp nuclei in pairs; or (3) of nuclei in vegeta- 

 tive cells where the archicarp is wanting or functionless 

 (Fraser, '07, '08, in Eumaria rutilans, fusion of the nuclei said 

 to take place soon after entering the ascogenous hyphae ; Car- 

 ruthers, '11, in Helvetia crispa; Blackman and Welsford, '12, 

 merely found evidence of nuclear fusion in vegetative cells of 

 Poly stigma ruhrum). 



^ Dangeard { '97 ) claims that the antheridium is functionless and that the 

 single nucleus in the oogonium divides into two. After his study of Pyronema 

 Claussen ('12) is inclined to question the fusion of the two sex nuclei in the 

 oogonium of Sphaerotheca, Erysiphe, Phyllactinia, and Pyronema as described 

 by Harper ( '95a, '96, '00, '05 ) , and by Blackman and Fraser ( '05 ) in Sphaerotheca 

 as well as in the case of Boudiera { = Ascodesmis) studied by him in 1905. In 

 respect to his work on Boudiera he now says : "My own statements upon the nuclear 

 fusion in the ascogone of Boudiera (Ascodesmis) are clearly wrong." He points 

 out that in none of these cases is the history of the nuclei in the ascogenous hyphae 

 known, and thinks that a reinvestigation will show paired nuclei here. A question 

 to be considered, says Strasburger ('05, p. 24), is whether the chromosomes of the 

 nuclei united in the oogonium do not remain in separated groups in the ascogenous 

 hyphae, in order to fuse as individual nuclei in the ascus. Lotsy ('07) has ex- 

 pressed a somewhat similar view in an attempt to harmonize the situation in the 

 Ascomycetes and Basidiomycetes. The fusion nucleus in the oogonium remains 

 for a time a 2x nucleus but some time prior to ascus formation the 2x nucleus 

 separates into two individual Ix nuclei in the ascogenous hypha, forming a syn- 

 karion. Conjugate division now takes place with ascus formation occurring 

 immediately or after several successive conjugate divisions. 



