THE MUTATION THEORY 347 
“Lamarck’s evening-primrose” (Fig. 57), says De Vries, “is a 
stately plant, with a stout stem, attaining often a height of 1.6 meters 
and more. When not crowded the main stem is surrounded by a large 
Fic. 57.—Oenothera lamarckiana, the original type used by DeVries in his 
experiments. This is the stock from Hilversum, from which arose in successive 
generations a series of mutants. (From De Vries.) 
