10 
Harris, A quantitative study of tlie factors influencing etc. 
base of the pod, tbe sigmas denoting the Standard deviations and 
the bars the means, we find for the two lots: 
NH Series 
4 ovules. 
w 
= 9.456 
+ 
.212 
P 
5 
ovules. 
w 
= 9.131 
+ 
.152 
P 
6 
ovules. 
w 
= 8.840 
I 
T 
.162 
P 
7 
ovules. 
w 
= 8,743 
+ 
.081 
P 
Series 
4 
ovules. 
w 
= 16.289 
+ 
.387 
P 
5 
ovules. 
w 
= 16.873 
+ 
.263 
P 
6 
ovules. 
w 
^ 16.821 
+ 
.198 
P 
7 
ovules. 
w 
= 16.658 
+ 
.171 
P 
8 ovules. 
w 
= 17.441 
+ 
.120 
P 
These lines and the empirical means are shown graphically 
in Diagrams 3 and 4. For both series the increase in weight 
front the base towards the tip of the pod is unmistakeable. It 
would be hazardous to say that any curve of a higher Order would 
describe the rate of change for the GG series better than a straight 
line. For the NH series, the straight line is clearly inadequate 
— the empirical means forming beautifully regulär curves. At 
first, the rate of increase is more rapid than is indicated by the 
straight line, later, it falls off and finally may actually decrease. 
The mean distal weight is in all four cases greater than the mean 
proximal. 
To test this matter of the form of the regression line 
somewhat more critically, the correlation ratio, y, which measures 
the intensity of interdependence between the magnitude of two 
characters when the y character (seed weight) does not increase 
at a linear rate with the x character (position in the pod). 
From the table it appears that the correlation ratio is some- 
times materially larger than the coefficient of correlation, but in 
general there is not much choice between them as descriptions of 
the interrelationship between the two characters. Blakeman’s 
test for linearity of regression 1 ) 
i f. _ 1 
i l-\- (1— if) 2 — (1 - r 2 ) 2 , 
Xi 
where I = j; 2 — r 2 and xi = • 67449 /)' N, applied to tkese individual 
yalues of r and y enables us to say whetker or not the ratio of 
change ma}^ be regarded as uniform (within the limits of the errors 
of sampling) from the base to the tip of the pod. Apparently, in 
most cases (e. g., in GG where the conclusion from Blakeman’s 
test is amply substantiated by the diagram) the straight line may 
p Blakeman, J., Biometrika. Yol. 4. 1905. p. 332—350. 
