S. 0. Harland 215 



It has been stated that difficulty is often experienced in distinguish- 

 ing tinged from some of the shades of rose, and therefore in classifica- 

 tion rose and tinged have been combined. 



It remains now to consider to what extent the hypothesis is sup- 

 ported by the experimental results. 



1. The expected F2. ratio of 10 rose and tinged : 3 green : 3 

 mahogany is closely approximated to in the actual results. 



2. Plants which were rose in F^. should exhibit four types of 

 behaviour in i^3 : 



(a) Breed true. 



(6) Segregate into rose and tinged, green, and mahogany in the 

 10:3:3 ratio. 



(c) Segregate into rose and mahogany in the 3 : 1 ratio. 



{d) Segregate into rose and green in the 3 : 1 ratio. 

 All these types of behaviour are demonstrated in the experimental 

 results, and the observed and expected ratios agree closely. 



3. Mahogany F^ plants should in F^ either breed true or segregate 

 into mahogany and tinged in the 3 : 1 ratio. No constant mahogany 

 families were observed ; both the families grown showed the ratio of 3 

 mahogany to 1 tinged. Had a larger number of families been grown, 

 some would no doubt have bred true to mahogany. 



4. Green F^ plants should in F3 either breed true or segregate into 

 3 green and 1 tinged. Owing probably to the small number of 

 families grown no constant greens occurred, but four families segregated 

 into 3 green and 1 tinged. 



5. Tinged F2, plants should breed true in ^3. This expectation was 

 realised in two families. 



6. The back-cross of F^ x green is of the nature MmGgxmGmG, 

 which should produce rose and green in the ratio 1:1. The observed 

 results agree closely with the expected. 



7. The back-cross of F^ x mahogany is of the nature MmGgxMgMg, 

 which should produce rose and mahogany in the 1 : 1 ratio. The observed 

 results again agree with the expected. 



To sum up : the hypothesis that two independently inherited Men- 

 delian factors are concerned in the cross green by mahogany, is con- 

 firmed by the experimental results. 



The two factors are : 



G. The factor for green, which converts tinged into green, and 



