No. 525] SEXUAL BEPRODUCTION IX FUNGI 543 



from the endokaryogamy in the ascus in the forms noted 

 by Guilliermond and Maire, and further we have no cases 

 as yet in which the binucleated condition originating in 

 a cell conjugation without nuclear fusion is working 

 forward into the sporophyte. In the full-cycled rusts the 

 binucleated condition and conjugate division extend from 

 the gametic union to the reduction stage in the spore 

 mother-cell. This is manifestly a condition of equilibrium 

 comparable to the stable conditions present in most 

 forms with definitely limited alternation of generations. 

 In Pyrunema in case Claussen's preliminary contentions 

 should turn out to be true the same condition would be 

 presented. We have nowhere evidence that the binu- 

 cleated condition and conjugate division originated in 

 gametic fusions and worked gradually forward through 

 the sporophyte. 



As perhaps the most striking evidence that the sapro- 

 phytic habit has not led to the disappearance of sexual- 

 ity we have the recent evidence as to the occurrence of 

 sexual fusions in the yeasts. It is probably too early to 

 speak with defmiteness as to nuclear phenomena in these 

 minute cells. Still there can be no question that in Zygo- 

 saccharomyces we have normal conjugation of gametes 

 followed by two divisions and spore formation quite 

 probably representing a reduction stage. In Saccharomy- 

 ces Ludwigii just as clearly a double division period and 

 endospore formation is followed by conjugation. This 

 transposition of the sexual stage may be secondarily de- 

 veloped as Guilliermond believes, or may indicate the 

 polyphyletic nature of the yeast group. There can at 

 least be no question that sexuality either in a primitive 

 or modified form has been maintained in this otherwise 

 highly specialized saprophytic group. 



Our knowledge of the conditions in the smuts as the 

 result of the work of Dangeard, myself, Federley and 

 Lutman, in a paper now in press, indicates that in this 

 group also two fusions may occur in a single life cycle 

 but under conditions which make the relations of the two 



