

Fio. 152. Diagram showing a method of double crossing maize to secure maximum yii'ld from seed 

 plot and general crop. Four different inbred strains (shown in the top row) are crossed in pairs, pro- 

 ducing the two vigorous but unrelated Fi hybrids shown in the middle row. IJy crossing these with 

 each other, an entire crop of Fi seed of high productiveness is secured. (After East and Jones.) 



