588 
Journal of A gricultural Research voi. xxvii, no. 8 
CORRELATION AMONG THE CHARACTERS OF THE PLANTS OF THE F 2 
The coefficients of correlation among all the characters of the plants 
of the second generation are given in Table X. Of these, the most in¬ 
teresting are those of negative sign, since they represent the cases where 
large dimension of one character is associated with a small dimension 
in the other. In most such cases the interaction of physiological fac¬ 
tors is eliminated, though there are several coefficients of negative sign 
which are purely mathematical in origin. Thus, the central spike index 
is of necessity negatively correlated with the length of the branching 
space, since the index represents the quotient obtained by dividing the 
length of the central spike by the sum of the length of the organ and the 
length of the branching space. There are others of a similar nature, but, 
considering the mass of coefficients in the table, they form a very small 
percentage. 
Height and total sucker height. —There are three significant 
disherences with height of plant, and two with total sucker height; but 
all of these can be discounted for physiological reasons. The non¬ 
linearity of the regression in the correlation involving height tends to 
reduce the coefficients, so that many of the coefficients not now in ex¬ 
cess of three times the error probably are significant. It is worthy of 
note that with several characters, such as length of the pistillate portion 
of the best inflorescence and the number of double female alicoles, where 
physiological and genetic factors are operating in opposite directions, 
the genetic relationships are strong enough to bring about negative 
correlations. 
