IX 



HEREDITY 



167 



The weight of the seed.— The inheritance of the 

 mean seed-weight is particularly interesting. In the first 

 place it fluctuates more than any other character, except- 

 ing the height, and it further shows clear evidence of 

 autogenous fluctuation. 



The first cross in which this character was carefully 

 examined was Afifi x Truitt (Fig. 66), where the mean 

 seed weights were 0-105 g. and 0-135 g. The seed weight 

 in Fj was 0"165 g. In Fa the weights ranged from O'OS 

 to 0'175 g., with two marked modes at 0-095 and 0-115. 

 The form of this Fj graph suggested that light seed was 



10 



- f, 



F16. 66. — Mean Seed-Wbight. 

 Afifi X Truitt, showing extraction of small seed in Fg. 



segregating from heavy seed, and on testing this by breed- 

 ing on, we found no reason to modify this conclusion ; 

 thus, a plant with seed weighing 0-100 regressed slightly 

 in F3 to a mean of 0-090, with a scatter from 0-070 to 

 0-110, and no higher probable error than the parent strain ; 

 and F4 raised from a 0-090 plant of these gave the same 

 result, ranging from 0-065 to 0-110. The plants of the 

 F4 had been extremely diversified in most other characters, 

 such as height, while the F4 was almost a pure strain. 



Whether the segregation was simple or compound, it 

 was clear that the size of the seed — expressed by us as 

 weight — was an inherited characteristic. 



In another cross, namely Charara x King (Fig. 68), the 

 matter became more interesting, and the inheritance 



