1916] DEV RIES—DIMORPHIC MUTANTS 253 
Fic. 2.—Oenothera Lamarckiana mut. cana: flowering spikes of the two types 
into which each generation splits; on the left the Lamarckiana type, on the right the 
parental type, showing the thin buds and the bent tips of the calyx; the difference 
in height of the 2 spikes is the same as the mean difference in height of the 2 groups 
on the bed; third generation of mut. cana no. 3, photographed July 22, rgr4. 
