A NEW THEORY OF THE ORIGIN OF SPECIES. 517 



to the presumption of mutation. H. de Vries. therefore, experimented 

 with 100 phmts that satistied this condition — centauries, asters. c3"no- 

 glossi, carrots, etc. He chose seeds from those which were distin- 

 guished by some peculiarity or deviation, liice fissuration of the leaves, 

 ramification of the spines, etc. He arranged for the sequestration of 

 the plant as soon as the peculiarit}' appeared, and ))efore tlowering. In 

 order to avoid hj'bridization he enveloped the floral beds with bags of 

 transparent parchment and fertilized the flower with its own pollen. The 

 greater number of his attempts failed. Onh^ one fully succeeded, that 

 which related to the onagra of Lamarck, the Oenothera lamarckiana. 



This plant is well known as the biennial onagra, or ass's herb, 

 brought from Virginia to Europe in 1613. It is a tufted, herbaceous 

 plant about a meter in height, with simple leaves bearing some resem- 

 blance to an ass's ear, whence the name of the plant. It has handsome 

 flowers, usually yellow in color. Its red tap root (red rampion) is 

 edi])le. Introduced into Holland, it became acclimated and is culti- 

 vated there; it also grows there in a wild or uncultivated state, escaped 

 from gardens and from cultivation. 



One species of this genus, the onagra of Lamarck {Oenothera 

 lamarcMana)^ was especially abundant around the little city of Hil- 

 rersum. Now, in 1875 it was noticed that in this district this species 

 showed unusual vigor and a remarkable power of multiplication and 

 dispersion. Varieties were multiplied in profusion, and there was, 

 therefore, reason to suppose that the plant was in its plastic crisis, in 

 its period of mutation. H. de Vries cultivated it in his experimental 

 beds at the botanical garden of Amsterdam, not for the purpose of 

 favoring the production of organic forms by means of culture, but 

 because by this means such forms could be preserved, aided, protected, 

 and given more chances of maintaining themselves. The sowings were 

 continued and the plants were observed during a period of fourteen 

 3^ears, from 1886 to 1900. In 1887 a new type made its appearance. 

 In 1888 there were already two new species. In 1900, after eight gen- 

 erations, H. de Vries had obtained, from 50,000 plants produced from 

 his several sowings, 800 new individuals belonging to 7 undescribed 

 species. There are, then, 800 individuals in 50,000 that are under- 

 going speciflc transformation. The activity of the mutation which this 

 plant exhilpits is, therefore, expressed b}^ 1\ per cent. 



The new species do not at all resemble the varieties of the parent 

 stock. They appeared suddenly, without preliminary or intermediate 

 forms. The care devoted to these experiments gives them a value 

 which must attract the attention of naturalists. Their result furnishes 

 a new and powerful argument in favor of the theory of mutation. 



