1910.] PUBLIC DOCUMENT — No. 31. 171 



only 6 show decided sliift. Counting the disagreements in rank 

 1)V nnits, the results are as follows: — 



111 vine lengths, ........ 16 



In pods per vine, ........ 20 



In peas per plant, .20 



These figures indicate once more the relative stability of the 

 vegetative character — vine length — as discussed in paragraph 

 2 above. 



COREELATION OF CHARACTERS. 



In former reports, some figures have been given on correlation 

 of character, jjarticularly between the average number of peas 

 per pod and the number of pods per vine. It might be supposed 

 that the vines bearing the largest number of pods would have the 

 smallest pods with fewest peas. The general fact seems to be the 

 contrary, — a fact which is of considerable practical importance 

 in the development of prolific strains and varieties. 



This year we have fresh figures at hand for three separate 

 groups. Series I. consists of a number of strains of Xott's Ex- 

 celsior, all having the same origin. They are, in fact, the same 

 plants spoken of as Strain A, Strain B, etc., in the experi- 

 ments reported herewith, p. 170, — the whole series being com- 

 bined for the purposes of this computation. Series II. is the 

 group of Xott's Excelsior from which the progenitors of Series 

 I. were selected in 1907. Series III. is a strain of Earliest of 

 All which we have had under study for two years. 



Taking this material, therefore, and computing the correla- 

 tion coefficients (in which complete correlation equals + 1 and 

 no correlation equals ) , we get the following results : — 



Correlation Coefficient.^ 



Series I. (Nott's Excelsior), . . . — .0081 ± .0012 

 Series II. (Nott's Excelsior), . . . + .1300 ± .0095 

 Series III. (Earliest of All), . . . +.3200^.0120 



1 It is probable that the coefiBcient of Series III. most nearly represents the true correlation, 

 and the lower coefficient for Series I. and possibly Series II. is due to rather strict selection that 

 has been practiced, Series I. being the second generation from 10 selected plants. See Pearson, 

 Phil. Transactions A, Vol. 193, p. 278; also Rietz, Biometrika, Vol. VII., p. 106. 



