7 8 TEXT-BOOK OF FUNGI 



only a single nucleus is present. Such a sequence occur- 

 ring among closely allied species seems to indicate the 

 gradual change from a primitive form, where numerous 

 nuclei in the oospore was general, to the more usual 



FlG. 27. i. Basidiobolus ranarnm, nuclei in beaks 

 becoming disorganised : the male nucleus has passed 

 into the enlarged female gamete, and has approached 

 the female nucleus (after Fairchild). 2-3, Dipodascus 

 albidus; 2, showing the mature ascus containing 

 numerous spores (after Lagerheim) ; 3, young ascus 

 of Dipodascus albidus, showing the one large nucleus 

 which by division forms the nuclei of the spores (after 

 Juel). All highly mag. 



condition met with at the present day when only one 

 nucleus is present. 



A somewhat primitive type of zygospore formation pre- 

 sented by Basidiobolus ranarum has been investigated in 

 detail by Fairchild. Two contiguous cells of an ordinary 

 vegetative filament each develop a protuberance or gamete. 



