66 



Plant Genetics 



63 : i ; the 63 reds as before falling naturally into differ- 

 ent groups on the basis of degree of redness. Applying 

 the same conception as before NILSSON-EHLE discovered 

 that in this case he was dealing with a trihybrid situation. 



Pure Red 



Grades of Pink 



White 



FIG. 15. Another method of visualizing NILSSON-EHLE'S 15:1 

 ratio (see fig. 14). 



Without constructing the usual Mendelian diagram, 

 which would have to be extensive enough for 64 indi- 

 viduals, the situation as it appeared in the F 2 generation 

 may be represented by fig. 16. If the graph is sur- 

 mounted by a curve we recognize the regular "proba- 

 bility curve," exactly the kind of curve biometricians 



