LEE BARKER WALTON 121 



may add new forms wHich really contain nothing new. 

 To build up and not to break down is the desideratum, 

 and the data obtained would seem to suggest that pure 

 line breeding with the employment of statistical methods 

 to show any progress would be the path leading most 

 directly to the goal. 



V. Conclusions 



1. Direct Conclusions 



The following conclusions drawn from the investiga- 

 tion are primarily statements of fact. 



1. Zygospores of Spirogyra in f lata (Vauch.) produced 

 by lateral conjugation or close breeding (quasi-partheno- 

 genesis) are relatively 26 per cent more variable in length 

 and 31 per cent more variable in diameter as measured 

 by the coefficient of variation, than those produced by 

 scalariform conjugation or cross breeding (sexual re- 

 production) . 



2. The size (volume) is greater in the average (mean) 

 zygospore close bred by lateral conjugation, where the 

 mean length is 62.38 fx. ± .178, than in the average zygo- 

 spore cross bred by scalariform conjugation, where the 

 mean length is 60.44 /a. ± .13 5. The diameter is approx- 

 imately the same in both types. 



3. In zygospores produced by lateral conjugation there 

 exists a positive correlation between length and diameter 

 of .1894 = .0460, while in scalariform conjugation the 

 value is .0934 = .0473. This is in general agreement with 

 results obtained by others although here the difference is 

 not significant when the probable error is considered. 



4. In the material studied approximately 45 per cent 

 of the zygospores were formed by lateral conjugation, the 

 remaining 5 5 per cent by scalariform conjugation. 



5. The material studied was strictly homogeneous, and 

 evidently arose from the same parental stock, both types 

 of filaments being intermingled with no structural dif- 

 ferences except those of conjugation. Consequently the 

 differences in variability are not the result of fluctuability. 



