434 THE AMERICAN NATURALIST [VOL. XLII 



in a purple mottled F l (PBM). It was the occurrence 

 of this purple mottled F 17 no matter which pigmented 

 bean was used, that led to my conclusions regarding the 

 latency of a mottled color-pattern and a melanizer in the 

 white bean, and also to the prediction that F 2 would 

 consist of the five forms purple mottled, black, brown 

 mottled, brown (more properly, dark orange), and white, 

 in the well-known tri-polyhybrid ratio, 27 : 9 : 9 : 3 : 16. 



AN UNEXPECTED RATIO AND ITS SIGNIFICANCE 

 At the time my last report was made, the count of the 

 F 2 hybrids had not been completed, but the five predicted 

 types were clearly presented. On summing up the results 

 of the census of the numerous F 2 hybrid families, it was 

 found that the ratio was not as predicted, but the mottled 

 and self-colored beans occurred in all cases in ap- 

 proximately equal numbers, resulting in the ratio 

 18 : 18 : 6 : 6 : 16, or, reduced to its lowest terms, 9:9:3:3:8. 

 To be exact, in the cross between Ne Plus Ultra (dark 

 orange yellow, called "brown" in my notes) and White 

 Flageolet, 10 families gave 133 purple mottled, 114 black, 

 40 brown mottled, 50 brown, 105 white, and 6 doubtful. 

 Similarly, in the cross between Long Yellow Six Weeks 

 flight yellow) and White Flageolet, 13 families gave 154 

 purple mottled, 159 black, 39 yellow mottled, 59 yellow 

 (or brown), 160 white, and 12 unclassified. In the cross 

 between Prolific Black Wax and White Flageolet, 3 

 families gave 53 purple mottled, 59 black, 44 white and 

 4 unclassified. 



On comparing these results with those published by 

 Tschermak 1 it is found that they are in perfect accord- 

 ance with them, as he also found in a number of similar 

 crosses, an equality between the mottled and self-colored 

 beans. But our conclusions were diverse as to the 

 source of the mottled pattern, I assuming that the mottled 

 factor was brought into the combination by the white 



1 Tschermak, E. Weitere Kreuzungsstudien an Erbsen, Levkojen ynd 

 Bohnen. Zeitschr. Landw. Versuchsw., 7, pp. 533-638, 1904. 



