[Vol. 2 



340 



A.RDEN 



are supposed to arise from an ascogonium in the base of the 

 ascocarp, but the nuclei are believed to arise from a haploid 

 nucleus. Conjugate division occurs in the ascus hooks, the 

 majority of which are formed by proliferation of the binu- 

 cleate penult cell and from fusions of the ultimate and ante- 

 penult cells of croziers, so that many conjugate divisions of 

 the haploid nuclei take place, and the first nuclear fusion is 

 in the ascus. In Laboulbenia chaetophora and L. Gyrinidarum 

 (Faull, Ml, '12) fusion of nuclei does not occur in the as- 

 cogonium, the mature binucleate ascogenic cell develops the 

 asci by budding, each ascus bud being preceded by a con- 

 jugate division of the nuclear pair. In Poly stigma rub rum 

 (Nienburg, '14) no fusion in the ascogonium occurs. In 

 Collema pulposum (Bachmann, '13 ) the nuclei in the ascogenic 

 cells were often found in pairs, but no cases of fusion were 



observed. 



(3). Forms in which an archicarp is absent or functionless, 

 and certain vegetative cells take on the function of ascogenic 

 cells, in which the authors believe nuclear fusion does not take 



pi 



Gnomonia erythrostoma (Brooks 



'10); Helvetia elastica (McCubbin, MO) in which the "as- 

 cogenous hyphae " form an intricately interwoven subhy- 

 menial layer of threads each with two nuclei in the end. The 

 ends of these hyphae form croziers with conjugate division of 

 the two nuclei followed by about six repeated proliferations 

 of the young ascus and crozier formations, accompanied by 

 fusions of the ultimate and antepenult cells and crozier 

 formation, resulting in many successive conjugate divisions 

 of the haploid nuclei, with fusion first in the ascus. In 

 Xylaria tentaculata (Brown, H. B., M3) the ascogenic cells 

 which appear to be derived by the separation of the cells of 

 "Woronin's hypha" are uninucleate and soon become multi- 

 nucleate by nuclear division. The nuclei multiply also in the 



ascogenous hyphae. 



The theory of a vegetative fusion in the ascus arose from 

 the belief on the part of some students that sexual fusion of 

 the nuclei occurred in the ascogonium, that the nuclear fusion 

 in the ascus must be a second fusion with no relation to the 



