THE MUTATION THEORY 477 



circle of smaller branches, growing upwards from its base so as to form 

 a dense brush The flowers are large and bright yellow attract- 

 ing immediate attention even from a distance. They open toward 

 evening, as the name indicates, and are pollinated by bumble-bees 

 and moths." 



On account of the classic character of De Vries's mutants of 

 Oenothera lamarckiana we shall follow his own detailed description 

 of the more significant of these. 



't>' 



NEW SPECIES (mutants) OF OENOTHERA'^ 

 HUGO DE VRIES 



This striking species {Oenothera lamarckiana) was found in a 

 locaHty near Hilversum, in the vicinity of Amsterdam, where it grew 

 in some thousands of individuals. Ordinarily biennial, it produces 

 rosettes in the first, and stems in the second year. Both the stems 

 and the rosettes were at once seen to be highly variable, and soon 

 distinct varieties could be distinguished among them. 



The first discovery of this locality was made in 1886. Afterwards 

 I visited it many times, often weekly or even daily during the first 

 few years, and always at least once a year up to the present time. 

 This stately plant showed the long-sought pecuHarity of producing a 

 number of new species every year. Some of them were observed 

 directly on the field, either as stems or as rosettes. The latter could 

 be transplanted into my garden for further observation, and the stems 

 yielded seeds to be sown under like control. Others were too weak 

 to live a sufficiently long time in the field. They were discovered by 

 sowing seed from indifferent plants of the wild locality in the 

 garden. A third and last method of getting still more new species 

 from the original strain was the repetition of the sowing process, by 

 saving and sowing the seed which ripened on the introduced plants. 

 These various methods have led to the discovery of over a dozen new 

 types never previously observed or described. 



Leaving the physiological side of the relations of these new forms 

 for the next lecture, it would be profitable to give a short description 

 of the several novelties. To this end they may be combined under 

 five different heads, according to their systematic value. The first 

 head includes those which are evidently to be considered as varieties, 



' From H. De Vries, Species and Varieties (copyright 1904). Used by special 

 permission of the publishers, The Open Court Publishing Company. 



