MUTATION IN THE EVENING PRIMROSE 



529 



the fuzz of a poach, sometimes arises as a ])rauch of the Peach 

 tree. 



Mutation in the Evening Primrose. — The Evening Primrose 

 is especially noted because it has furnished nmch of the material 

 upon which the nmtation theory is founded. One of the diffi- 

 culties in finding mutations is that any given species does not 

 mutate all of the time but only at occasional periods. In 

 1886 De Vries began to search for sjoecies that were in the 

 mutating period. The 

 American Evening Prim- 

 rose (Oenothera Lamarck- 

 iana) {Fig. Jf72), also 

 known as La m a r c k ' s 

 Evening Primrose, proved 

 to be the species for which 

 he was searching. He 

 found a large number of 

 plants of this species 

 growing in an abandoned 

 potato field at Hilversum, 

 near Amsterdam. Among 

 them he found some un- 

 known and very distinct 

 forms which apparently 

 had come from seeds of 

 the normal American 

 Evening Primrose. Seeds 

 were secured from the 

 normal plants, and cul- 

 tures were begun in the 

 Botanical Garden at the 

 University of Amsterdam. From the first soAving he obtained 

 •another new form. Through a series of pedigree cultures in- 

 volving a number of generations, quite a number of distinct 

 forms were obtained. Some of these distinctly new forms ap- 

 peared repeatedly in the cultures, while others appeared only 

 once, but they all bred true, thus producing offspring like them- 

 selves. These new forms did not arise gradually but appeared 

 suddenly and were so distinct fi'om the American Evening 

 Primrose, their parent, as to hv calked new species. 



Fig. 472. — Lamarck's Evening Primrose 

 {Oenothera Lamarckiana) , a mutating 

 species. After De Vries. 



