THE MUTATION THEORY 



347 



'Tamarck'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. — Oenothera lamarckiana, the original type used by De\'rics in his 

 experiments. This is the stock from Hilvcrsum, from which arose in successixc 

 generations a series of mutants. {From De ]'ries.) 



