The Plant World. 



mass. In 1902, 19 pure lines were planted for weight studies. 

 Inside of each pure line, selections were made of some of the med- 

 ium weight bean seeds, but particularly of the seeds near the 

 extremes. The following table gives the data of one line. All 

 weights are in milligrams. 



Weight of grandmother bean (1900): 270 

 Mean weight of the mother seeds (1901): 510 



Weight Classes of the 

 mother seeds (1901). 



200-250 

 450-500 

 600-650 



The entire line 



Characters of the OfiFspring (1902). 



Mean Weight. 



469 

 446 

 450 



449.5 



No. of Seeds. 



18 



131 



39 



188 



Standard 

 Deviation. 



59.4 

 68.1 

 63.7 



66.3 



Fig. 2. Relation of offspring to parent bean seeds in regard to weight, as studied by 

 Johannsen in a population. The ntunbers at the ordinates and abscissae in this and the 

 following figures represent centigrams while the numbers on the mean lines represent milli- 

 grams. 



Each of the 19 pure lines was treated in this manner and 

 in several cases more weight classes were used for each line. If 

 we take the mean weights of the mother classes and the mean 



