190 



HEMIBASIDIOMYCETES 



[CH. 



Federley.in 1903, described specimens of this fungus in which conjugation 

 is followed not only by the migration of the nucleus of one of the cells 



concerned, but also by nuclear 

 fusion (fig. 155). In view of 

 the fusion in the young spore 

 recorded by Dangeard and by 

 Ravvitscher the details of de- 

 velopment in this species de- 

 mand further investigation. 



Ustilago Maydis, the smut 

 of Zea Mays, induces con- 



F'g- '5r- Ustilago Tragopogonis pratensis (Pers.) Wint. ; siderable hypertrophy. The 

 conjugation and nuclear fusion ; after Federley. , r . . 



deformations contain a mass 



of gelatinous mycelium from which brand-spores are produced. When 

 mature, the spore mass causes the rupture of the enclosing tissues, and the 

 spores escape. They germinate to produce basidia from which uninucleatc 

 basidiospores are abstricted. These in turn multiply by budding, but, accord- 

 ing to Rawitscher, they never conjugate, nor do they form a definite mycelium 

 (fig. 156*7). In the infection of the host plant, hyphae are for the first time 

 developed, and, unlike those of most investigated smuts, consist of uninu- 

 cleate cells (fig. 156^). This is the case even when the hyphae begin to 

 break up in preparation for spore-formation. At this stage, however, the ends 

 of adjacent cells are seen to become swollen where they are in contact, the wall 

 separating their protoplasm breaks down, the two nuclei come together in 



Fig. 156. UMagoMaydis\ a. basidiospores, x 54 o; b. uninucleate mycelium x 4 2 O ; 

 after Ravvitscher. 



