488 



BOTANICAL GAZETTE 



[JUNE 



Vaucher has figured 6 species of Spirogyra, 2 of which are shown 

 in scalariform conjugation and 4 in cross-conjugation. I have 

 arranged these species in table I so that the methods of reproduction 

 assigned by the different writers may be compared. 



TABLE I 



Species according 

 to Vaucher 



Method of reproduction 



Vaucher 



Allongee Scalariform 



Wolle 



DeToni 



Adherente 

 Majeure. . 

 Portiquis. 

 Condensee 

 Renflee . . . 



Scalariform 



Cross 



Cross 



Cross 



Cross 



Scalariform 



Scalariform 



Scalariform 



Scalariform and aplanospores 



Scalariform 



Scalariform and lateral 



Lateral 

 Not stated 

 Not stated 

 Not stated 

 Often lateral 

 Often lateral 



At first glance there does not seem to be much uniformity, but 

 if we assume that where DeToni does not state the particular 

 method of conjugation that the scalariform method is meant, we 

 find that Wolle and DeToni agree that 5 of these species have 

 scalariform conjugation. They also agree in assigning lateral 

 conjugation to renflee. However, DeToni alone states that con- 

 densee conjugates laterally, while Wolle alone states that portiquis 

 forms aplanospores. In these 3 cases, therefore, it would be 

 possible to have combinations with the appearance of cross- 

 conjugation. Majeure, however, according to both Wolle and 

 DeToni, conjugates only in the usual scalariform manner- Figur- 

 ing this species in cross-conjugation by Vaucher is rather surpris- 

 ing, as will appear in the discussion which follows. 



Since there have been but few cases of cross-conjugation 

 reported, we have reason to doubt its occurrence in as many species 

 as figured by Vaucher. Furthermore, no other observer up to 

 the present time has recorded its occurrence in any of these 

 species. However, the species discussed in the present paper has 

 been tentatively identified as S. inflata (Vauch.) Rahb., which 

 according to Rahbenhorst would include Conjuguee renflee of 



Vaucher. 



Recognizing, then, the facts that (i) Vaucher was unac- 

 quainted with lateral conjugation, (2) a combination of lateral 





