Vol. 2 No. 6 



TORREYA 



June, 1902 

 THE ORIGIN OF SPECIES BY MUTATION* 



By D. T. MacDougal 



As a result of previous studies, de Vries was led to believe that 

 species with a tendency to form monstrosities would be most 

 likely to offer opportunities for securing evidence of the origin of 

 new species by mutations or discontinuous variations. A thor- 

 ough inspection of promising forms around Amsterdam in Hol- 

 land was begun in 1886 and carried on for several years, during 

 which period more than a hundred species were brought under 

 cultivation, only one of which was found useful for observations 

 upon mutations. 



The plant in question — Onagra biennis (L.) Scop. \Oenothera 

 Lamarckiand\ — had escaped from cultivation in this locality in 

 1875 and was represented by several hundred examples in an old 

 potato field. The rapid multiplication of the individuals had 

 been accompanied by many divergences from typical forms inclu- 

 sive of ascidia and fasciations, and while many were annuals, others 

 were clearly biennial and a few were triennials. In 1887, a num- 

 ber of individuals representing two forms so distinct from 0. 

 biennis as to constitute new elementary species were found in the 

 multitude of individuals which were examined. The exact origin 

 of the new types, which were named Oenothera brevistylis and 

 Oe. iaevifolia, could not of course be determined, but both were 

 found to be constant from seeds ; furthermore, no examples of 

 similar forms could be found in the principal herbaria. The oc- 

 currence of the two forms in question was not conclusive evi- 

 dence in itself but they served to bring the interest and enthu- 



* Continued from page 68. 



[The exact date of publication of each issue of Torreya is given in the succeed- 

 ing number. Vol. 2, No. 5, comprising pages 65-80, was issued May 14, 1902.] 



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