172 EXPERIMENT STATION. [Jan. 



In Series I. no relation between nnmber of pods and peas per 

 pod is shown. In Series 11. there is exhibited a distinct ten- 

 dency toward the production of the largest and fullest pods on 

 those plants which produce at the same time the largest num- 

 ber of pods ; and this tendency becomes fairly emphatic in 

 Series III. 



Heeedity in Peas. 



One of the prime objects in this series of experiments has been 

 the study of heredity. We have wanted to know in what degree 

 the various characters were transmitted in peas. Some figures 

 in this field were published last year.^ The figures this year are 

 still more interesting, especially when compared with last year's 

 results. 



The reader may know that heredity is now commonly calcu- 

 lated by a mathematical formula which gives results theoretically 

 varying between + 1 and — 1 (practically between + 1 and 0). 

 Ordinary inheritance, in which parental characters are trans- 

 mitted in the usual degree, will show a coefficient of +.25 to 

 +.40. Larger coefficients are rare ; lower coefficients are sur- 

 prisingly frequent. Taking our peas in Series I. (omitting 

 Strain C on account of its abnormal character), we secure the 

 following heredity coefficients from the crop of 1909 : — 



Coefficients of Heredity. 



Vine length, + .24S3 ± .01G4 



Pods per vine, + .0792 ± .0017 



Total peas per vine, + .0544 zt .0018 



Here it will be seen that vine length is transmitted much more 

 fully than either of the other characters. This fact is apparently 

 closely related to the one mentioned above (p. 170). The vegeta- 

 tive character is more stable and is more jDcrfectly transmitted 

 than the reproductive characters. 



Peepotency. 

 In all old-time discussions of heredity, much was made of 

 prepotency. Though this word and the idea have to a large 

 extent been submerged in recent discussions of plant breeding, 



' Massachusetts Experiment Station Report, 21, p. 171 (1900). 



