76 GENETICS AND EUGENICS 



is confined to one evening and the following morning, but in 

 cloudy weather they may remain open longer. 



When De Vries discovered this plant growing wild in 1886 

 he was struck by its variability. It seemed to be producing, 

 in the isolated spot where he found it, new species, the thing 

 for which De Vries had long been looking. He says : 



I visited [the spot] many times, often weekly or even daily during the 

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

 [eighteen years later]. This stately plant showed the long-sought peculi- 

 arity of producing a number of new species every year. Some of them were 

 observed directly in the field, either as stems or as rosettes [young plants in 

 their first year's growth]. 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 plants of the wild locality. 



By these means over a dozen new types were discovered 

 never previously observed or described. De Vries has given 

 to these distinctive names; some of them he regards as true 

 species, others merely as varieties; the basis of his distinction, 

 an arbitrary one, does not concern us. The peculiarity of the 



TABLE 5 



Some Mutants of Oenothera Lamarckiana 



1. Smooth-leaved (laevifoHa) | 



2. Short-styled {brevistylis) \ Retrogressive or Loss variations. 



3. Dwarf (nanella) J 



4. Giant {gigas) 



^ , . , / , . . X f Progressive or Gain variations. 



5. Red-veined {riibnnervis) j 



6. Pale-leaved (albida) 1 t^ 1 1 ^ ^ 



_ , , , , / , , N r ^ eeble mutants. 



7. Oblong-leaved {oblonga) J 



case is, not that a group of undescribed species or varieties 

 was found growing together, but that they were produced 

 year after year from the seed of the parent species, and from 

 their first origin bred true (in most cases) to their distinctive 

 characters. 



One of the mutants was distinguished by its smooth slen- 

 der leaves (laevifolia) ; another by the short style of its 

 flowers (brevistylis) ; a third by its dwarf habit {nanella, Fig. 

 26), one-fourth the height of the parent species. All three 

 bred true to these peculiarities which De Vries considers due 



