DE VRIES'S THEORY OF MUTATIONS. 215 



The third mutation, called Oenothera oblonga, repeatedly occurred 

 (350 specimens) in the series of generations of CEnothera Lamarckiana 

 that were successively cultivated. Many hundreds were cultivated 

 later. It may be recognized with certainty as soon as the sixth leaflet 

 unfolds, and has remained unchanged, with the exception of two speci- 

 mens, which, however, have not retroceded towards 0. Lamarckiana, 

 but showed the characteristics of 0. albida and 0. rubrinervis. This 

 mutation has thus, although perfectly stable, retained the power to 

 further mutate. 



The fourth mutation, CEnothera rubrinervis, again shows other in- 

 teresting peculiarities. It is a strong plant, not less rich, both in 

 pollen and in seed,* than 0. Lamarckiana, which was more or less the 

 case with the other mutations. It has been obtained in very great 

 numbers (2,976 specimens) by de Vries, and the stability of CEnothera 

 rubrinervis has asserted itself most distinctly also for all those speci- 

 mens that had descended from different mother plants. 



The fifth mutation, 0. nanella, differs from the others in the fact 

 that its deviation from the original 0. Lamarckiana does not show 

 itself in a given number of sharply determined and constant char- 

 acteristics, but only in one, its dwarfed dimensions. Thus we should 

 be inclined to look upon 0. nanella rather as a variety than as an ele- 

 mentary species. However, in this case the smaller dimensions do not 

 come under the head of fluctuating variability, but we have undoubt- 

 edly an unmistakable mutation that can be recognized as such with 

 certainty as soon as the second leaf begins to show itself, and which, 

 when fecundated in 1893 by its own pollen, directly produced 440, and 

 in 1895 2,463 germinating plants, all of them, without exception, 

 CEnothera nanella. In 1896 the seeds of 36 other plants of 0. nanella 

 were again planted and 18,000 seedlings were obtained, which again 

 showed, with perfect precision, the characteristics of the species, with 

 the exception of three mutating plants that bore at the same time the 

 distinctive characters of O. oblonga, and thus formed an elementary 

 species of the second degree, O. nanella oblonga. 



We have yet to mention two mutations, O. lata and O. scintillans. 

 The first only consists of female plants; there is never any fertile 

 pollen produced, so that its stability can not be made out with certainty. 

 The second, a dark green plant with shining leaves, is a rare mutation, 



* It should here be mentioned that de Vries has noticed (I. c, p. 186) that 

 the seeds of mutating plants generally retain the power of germinating for a 

 longer period than the seeds of the normal O. Lamarckiana. Upon this fact 

 he bases the expectation that perhaps later it will be possible to utilize this 

 peculiarity and to find means to increase the percentage of mutating plants 

 in a given series of sowing experiments by artificially somewhat accelerating 

 the dying off of the seeds. This might also prove important when searching for 

 mutations. 



