1917] CUNNINGHAM— SEXUALITY OF SP1R0GYRA 491 



munication 



enomenon 



more 



than half a dozen cases of it. However, he sees 

 no reason why it should not occur, as it represents much the same 



enomenon from 



In 



must 



will 



Coulter (10, p. 40) briefly describes cross-conjugation but 

 does not assign it to any species. 



On the other hand, the great majority of botanists doubt the 

 occurrence of cross-conjugation, and with it the bisexuality of the 

 Spirogyra filament. Agardh (i), according to Hassall (15), 

 states that one filament is always giving and the other always 

 receiving. Wood (32) mentions scalariform and lateral conjuga- 

 tion, but not cross-conjugation. Cooke (9) has 11 plates of 



Spirogy 



DeBary (ii) 



states that one filament gives and the other receives. Wolle 

 (31) figures and describes 39 species of Spirogyra, citing Vaucher 

 and Hassall, but does not mention cross-conjugation. Haber- 

 landt (14), according to Klebs, holds that the filaments are 

 distinctly sexual. In order to verify this statement, Klebs (22) 

 grew Spirogyra on nutrient agar, but found that a filament would 

 not conjugate with itself, and therefore concluded that it was all 

 of one sex. This experiment might prove the case for one species, 

 but it hardly appears just to use it as the basis for a sweeping 

 statement that bisexuality does not occur in Spirogyra. Mottier 

 (24) cites this experiment as a basis for belief in the unisexuality 

 of the filament. DeToni (12) absolutely ignores cross-conjugation, 

 although he cites the plates of both Vaucher and Hassall in 



his descriptions of the species figured in this condition by them. 

 Lotsy (23) states that there is a distinct difference between the 

 male and the female filaments. Oltmaxns (25, p. 64) states 

 specifically that we have to do with male and female filaments. 

 Hertwig (19) makes a similar statement. Engler and Prantl 

 (13) speak of the visible difference between the male and female 

 filaments. Robertson (26), who grew Spirogyra extensively 

 under abnormal conditions, did not find a case either of cross or 

 lateral conjugation. Since cross-conjugation did not occur in his 



