No. 525] SEXUAL REPRODUCTION IN FUNGI 537 



tory in the cells from which the basidium arose. Such a 

 process was entirely unknown before in either plants or 

 animals. 



Subsequent investigations by Dangeard, Maire, Ruh- 

 land, Nichols, myself and others have shown that in the 

 Basidiomycetes a long- series of binucleated cells pre- 

 cedes the formation of the basidium and the nuclear 

 fusion in it may well have something- of the value of a 

 union of differentiated gametic nuclei. 



The origin of the binucleated cells in the Basidiomy- 

 cetes does not apparently re>ult from a cell fusion at a 

 definite point in the life cycle, as is the case in the a?cid- 

 ium of the rusts. Such a fusion might perhaps be ex- 

 pected to be effected at the origin of the carpophore, but 

 it has been established that binucleated cells may be 

 present in the mycelium prior to the formation of the 

 carpophore. Series of such cells may extend back almost 

 if not epiite to the germination of the spore from which 

 the mycelium arose. 



A fusion of gametes morphologically equivalent to 

 those of other algae and fungi seems to have quite disap- 



it is to be remembered that comparatively few forms 

 have been investigated as to the early stages of the for- 

 mation of the carpophore. It seems probable that the 

 endokarygamy in the basidium may have functionally 

 replaced an older fusion of differentiated sex cells. 



"\Ve have then on the present evidence a large group 

 (over 9,000 species, according to Saccardo) of sapro- 

 phytic and parasitic organisms in which normal sexual 

 reproduction has been replaced by the fusion of nuclei 

 of probably separate descent through a long series of 

 cells, but which are contained at each stage within the 

 limits of a single cell body. 



The most, thoroughly worked out modification of sexual 

 reproduction in the fungi is the fusion of uninucleated 

 gametes producing binucleated series of cells in which 

 nuclear fusion follows only at a much later period. Such 



