SEXUAL REPRODUCTION 91 



the conjugated cell, whereas its apical portion containing 

 two nuclei is cut off by a transverse wall, and constitutes 

 the first aecidiospore mother-cell. This cell at once 

 divides into two unequal cells, the aecidiospore and the 

 small intercalary cell. After one aecidiospore has been 

 formed, the nuclei in the basal conjugated portion again 

 divide, another aecidiospore is cut off, and by a repetition 

 of this process a chain of aecidiospores is formed in basi- 

 petal succession. Probably when a greater number of 

 species are examined, apparent discrepancies as to the 

 method of forming a binucleate cell, as described by 

 Blackman and Christman respectively, may be explained. 



Dangeard's ideas respecting sexuality in the higher 

 fungi are as follows. The higher fungi consist of two 

 principal branches, Basidiomycetes and Ascomycetes, in 

 which sexual reproduction is uniform throughout. The 

 Basidiomycetes are subdivided into the Ustilagineae, 

 Uredineae, Protobasidiomycetes, and Basidiomycetes. 



In the Ustilagineae the young cells of the mycelium are 

 binucleate ; older cells may contain more than two nuclei. 

 The formation of asexual conidia reduces the cells to a 

 uninucleate condition for the time being. In sexual 

 reproduction the cells become swollen or give off vesicular 

 branches; the two nuclei of each cell are of different 

 origin. Each swollen cell with its two nuclei should be 

 considered as a gametangium containing two uninucleate 

 gametes, each nucleus having lost the power of dividing as 

 in an ordinary gamete. The two gametes combine to form 

 one by the fusion of the two nuclei. The reserve material 

 accumulated in the swollen cell constitutes an oospore 

 which increases in size, and becomes surrounded by a thick 

 membrane consisting of an epispore and an endospore. 



