152 Plant-Breeding 



the parentage and the related group that constitutes 

 the offspring." 



The coefficient of heredity. The degree of inheritance 

 between a parental group of plants and their corresponding 

 group of offspring is determined by the use of a correlation 

 table. The degree of correlation or the resemblance is 

 determined between the parents and offspring. This may 

 be expressed mathematically and the result is known as 

 the "coefficient of heredity." The latter is, therefore, 

 nothing more nor less than the correlation coefficient (r) 

 obtained from a table in which two sets of individuals 

 related by descent are tabulated with respect to the same 

 character. The coefficient of heredity is expressed as a 

 decimal, somewhere between and 1. The nearer 1, 

 the greater the closeness of resemblance between parents 

 and offspring, and conversely the nearer 0, the smaller 

 the degree of resemblance. 



In the table (pp. 150-151) will be found the number of 

 tubers in hills of potatoes in 1909 as compared with the off- 

 spring from these hills in 1910. For example, there were 3 

 hills of seedling potatoes having either 7 or 8 tubers in 1909 

 represented in the table by the midpoint 7.5 which gave 

 offspring in 1910 having either 3 or 4 tubers (3.5) ; 8 

 parental hills numbering either 7 or 8 tubers in 1909 which 

 produced offspring in 1910 having either 5 or 6 tubers ; 

 11 parental hills having the same number of tubers as 

 above which produced offspring having either 7 or 8 hills, 

 and so forth for each number in the table : 

 Notation. 



n = Total number of individuals in the population, 

 equals summation of all frequencies. 



