SEXUALITY OF FILAMENT OF SPIROGYRA 1 



Bert Cunningham 



(with plates xxiii-xxv) 



Is the filament of Spirogyra unisexual or bisexual ? This has 



* 



been a question for many years, but the reports of the great majority 

 of modern workers would indicate that they regard the filament 

 as wholly of one sex. The answer to the question hinges upon the 

 presence of zygotes in both of the conjugating filaments. If they 

 occur in only one of the two, the filaments may be said to be 

 unisexual, since one functions as the male and the other functions 

 as the female; if, on the other hand, they occur in both filaments 

 and are formed by scalariform conjugation, the filaments may be 

 said to be bisexual, since the empty cells in each have furnished 

 the male gametes, while the ones in which the zygotes occur 

 previously contained female gametes. The latter case is known 

 as cross-conjugation. 



The advocates of the theory of the unisexuality of the filament 

 urge that as a rule all the male gametes arise in one filament and 

 pass over into the other, so that zygotes appear in but one of the 

 two conjugating filaments. They urge also that cases of cross- 

 conjugation are so rare that they should be considered abnormal- 

 ities and the result of forced conditions. Strangely enough they 

 ignore lateral conjugation in so far as the sexuality of the filament 

 is concerned. On the other hand, those who do not accept this 

 theory have taken two different positions: one, that the gamete is 

 absolutely sexless (Hassall 17, p. 130; also Pringsheim, see 

 Bennett 2) ; and the other, that the filament is bisexual, based 



1 This work was done in the Biological Laboratory of Trinity College, Durham, 

 North Carolina, under the direction of Dr. J. J. Wolfe. The writer wishes at this 

 point to thank Dr. Wolfe for his many kind and helpful suggestions. He further 

 desires to acknowledge aid rendered on special questions arising in the course of the 

 work by Professor G. S. West, of the University of Birmingham, England, and 

 Professor J. M. Coulter, of the University of Chicago. Thanks are due also to 

 Mr. J. P. Breedlove, librarian of Trinity College, for his great assistance in securing 

 literature on the subject. 





Botanical Gazette, vol. 63] 



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