Oenothera Lamarckiana and O. gigas . 971 
grains of gigas are much larger than those of Lamar ckiana, thus supporting 
the view that in related types the size of the cells and nuclei are propor¬ 
tionate to the number of chromosomes. 
16 . Oenothera gigas is a progressive mutant, its peculiarities being 
clearly associated with the changes in its germ-plasm incident upon the 
doubling of its chromosome number. 
Cambridge, Massachusetts, 
March , 1911. 
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