90 



Plant Genetics 



is coupled with a similar one, in other strains become 

 coupled with its opposite (its allelomorph) ? This is a 

 theoretical difficulty which will be cleared up when we 

 consider the next topic. It will be realized that genetics 

 as yet represents an accumulating mass of data in 



Parents 



Parents 



Only 2 Gametes 



Possible 

 F, Gives 3 : 1 Ratio 



ANTAGONISnC CHARACTERS" 



Only 2 Ganietn 



Possible 

 F, Gives 1:2:1 Rabo 



Fig. 23. — Diagram showing how coupled and antagonistic char- 

 acters might be explained by the same mechanism. 



reference to the facts of inheritance, and also an ac- 

 cumulating mass of speculations as to the explanations 

 of the facts. The facts are undoubted, while the specu- 

 lations suggest further experimental work. 



9. Linkage and crossing over. — Emerson con- 

 cluded his original work on coupled and antagonistic 



