118 THE THEORY OF THE GENE 



together, as Winkler at one time thought probable, but 

 it seems more likely that the tetraploids arise by the sup- 

 pression of the cytoplasmic division of a dividing cell, 

 which would thereby double the number of its chromo- 

 somes. Such a tetraploid cell might form the whole or 

 only the core, or any other part of a young plant. 



A tetraploid of the common Jimson weed (Datura 

 stramonium) (Fig. 72 below) was found by Blakeslee, 



Fig. 72. 

 Diploid plant of Datura stramonium, above, and tetraploid, below. 



(After Blakeslee.) 



