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 



FIG 57. Ocnothera 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,) 



