434, Mr Engledow, A Case of Repulsion in Wheat. 
If repulsion occur on a 1 : 3::3:1 basis between “Roughness” | 
and “ Blackness,” the theoretical expectation for this case is: | 
4 i 
109°8 49:9 49-9 33 
The results of the single character classifications are as follows: 
Rough : Smooth :: 163 : 50 
Black : White :: 167 : 46 
the expectation being in each case 160 : 53. The probable error| 
of the number of dominants is 4°3 and hence the agreement with} 
expectation is satisfactory. 
In another note* there appears a method of determining the! 
best coupling or repulsion series for a set of observed data. | 
Employing that method for this case, the best series is found | 
to be: | 
Ihe DRG) 22 DENG 2 IL. 
In the paper already referred to, the results are examined by! 
Pearson’s Method+ for the probability of the fit of an observed to! 
an expected series. It is apparent from the examination that the| 
probability of the existence of repulsion on the 1:3 ::3: 1 basis! 
between “Roughness” and “Blackness” in wheat is quite asi 
great as that of the existence of coupling and repulsion which has}! 
been described in the cases of other plants. 
A point of some interest lies in the fact that blackness appears’ 
not to be a simple character—not simple in the sense of not being | 
present always to the same extent. Some of the second generation | 
plants are so black that they are indistinguishable from the black | 
parental type, while others show merely a small black patch on| 
the glume. The interval between these extremes is fairly | 
uniformly filled by plants of intermediate blackness. It must, 
however, be remarked that blackness when present is readily, 
detected. White glumed plants which have been discoloured by, 
disease sometimes resemble plants with small black patches but) 
the patches caused by disease are not similarly placed on all the 
glumes of the ear and they may be almost completely removed by’ 
scraping gently with a sharp knife. | 
The presence of blackness to so varying a degree can with’ 
difficulty be conceived to be produced and controlled by one. 
factor only. One factor or combination of factors common to all! 
the black plants and accompanied in some cases by an intensor or! 
partially inhibitor factor is the explanation which at once suggests | 
itself. 
b) b) ? 
mination of the Best Value of a Coupling Ratio from a given set of data.” 
+ Pearson, Phil, Mag. vol. u, 1900, 
* Yule and Engledow, Proc. Camb. Phil. Soc., Vol. xvu., Part 5, ‘‘The Deter- 
