iQie] 



DeVRIES— DIMORPHIC MUTANTS 



275 



the mean for each group in the last columns of the table, and the 

 reHabiUty of this mean evidently depends strongly on this fact. 



TABLE XH 

 Splitting into laeia and velutina 



Theoretically a spHtting into 4 groups of equal size should be 

 expected, namely into cana-laeta, cana-velutina, laeta, and velutina.^' 

 Evidently one of the first two groups is suppressed. This con- 

 clusion holds good for 0. cana just as for 0. scintillans , but in the 

 case of 0. lata the fourth group is sometimes visible, a few speci- 

 mens of the /flto-like hybrids assuming at the same time the marks 

 of 0. laeta (about i per cent, Gruppenweise Artbildung, p. 255), 

 whereas the remainder are clearly lata-velutina. It is probable 

 that the same groiip is suppressed in both the other cases, and for 

 the same reasons, which are as yet unknown. The fact that there 

 are so often more velutina than should be expected probably has 

 the same cause as the exuberant occurrence of this form in the 

 crosses of 0. Lamarckiana (82 per cent). The analogous crosses 

 of 0. nanella, given in the lower part of the table, show that these 

 "De Vries, Hugo; On triple hybrids. Bot. Gaz. 47:1-8. 1909. 



