352 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



[Vol. 2 



hyphae. — A moderately large number of species, in which 

 more or less extensive sterilization of the terminal portion of 

 the archicarp has occurred, have been examined by cytological 

 methods and in most cases a reduced or modified sexual con- 

 dition has been found. 



In Pyronema confluens great variations occur in the sexual 

 nature of the ascogonium. In what may be called normal 

 cases, antheridial nuclei enter and become associated with the 

 ascogonial nuclei (Harper, '00; Claussen, '07, 12). Under 

 cultural conditions the antheridium may be normal, rudi- 

 mentary or absent, but the ascogonium develops in a normal 

 manner (van Tieghem, '84). Different strains may also be- 

 have differently. In some the antheridium does not fuse with 

 the trichogyne, while in others it does (Brown, W. H., '09). 

 In some cases even when the antheridium fuses with the 

 trichogyne, its nuclei do not pass into the ascogonium (I)an- 

 geard, '07), but degenerate in situ (Brown, W. H., '09). In 

 these cases where the antheridium does not function the sex- 

 uality of the ascogonium is modified in as much as its nuclei 

 are differentiated sooner or later so that in pairs they per- 

 form the function of sperm and egg nuclei. According to 

 W. H. Brown ('09) in cases where the origin of the pair of 

 nuclei in the ascus hook could be determined, they were sisters. 

 After the one conjugate division in the hook the two nuclei 

 in the ascus, or penult cell, are "cousin" nuclei. 



The archicarp of Lachnea scutellata (Woronin, '66; Brown, 

 W. H., 11) consists of about nine cells. No antheridial struc- 

 ture has been observed. The penultimate cell functions as 

 the ascogonium (Brown, W. H., 11). It is multinucleate and 

 no fusion of nuclei in pairs takes place here. The nuclei are 

 increased in numbers by division, not only in the ascogenous 

 threads where they do not appear to be paired or show con- 

 jugate division, but also in the ascus hook where conjugate 

 division takes place. The numerous fusions of the terminal 

 and basal cells of the ascus hook result in numerous succes- 

 sive conjugate divisions. In Leotia, although the archicarp 

 has not been clearly observed, it would appear from the ac- 

 count (Brown, W. H., 10) that the antheridium is absent (or 



