394 



THE FUNGI WHICH CAUSE PLANT DISEASE 



nucleus b}^ two mitoses gives rise to four nuclei which wander 

 through the sterigmata into the spores and constitute the four 

 basidiospore nuclei. 



The significance of this phenomenon of fusion in the basidium 

 followed by division, which is wide spread and apparently the 



M 



NO P 



"0 l,0^.fl N:^ ^^ f^ 





ff 



/^: 



m 



A 7 ^#) ^ 



8» 



f Id. 283. — Stages in the development of the basidium (Agaricus) ; original 

 binucleate condition, followed (E-F) by fusion, and subsequent mitosis N-R, 

 resulting in four spore nuclei. After Wager. 



dominant typical phenomenon among the Basidiomycetes includ- 

 ing both high forms, Agarics, ^^ and low forms, Dacryomycetes,'* 

 the Uredinales "*' ^^' ^^^' '^'' '^^ and even the Gasteromycetes 

 (Maire),''' is much debated. By some it is regarded as a very 

 much modified type of fertilization, a view to which support is 

 lent by the fact that in some of these fungi, perhaps all, the 

 nuclei multiply by a process of conjugate division. Thus the two 

 nuclei found in the yoimg basidium, although belonging to the 

 same cell may in ancestry be very distantly related. 



