700 Mutations 



saw it, seventeen years ago. How long had 

 it been so? Had it commenced to mutate after 

 its introduction into Europe, some time ago, or 

 was it alread}^ previously in this state! It 

 is as yet impossible to decide this point. Per- 

 haps the mutable state is very old, and dates 

 from the time of the first importation of the 

 species into Europe. 



Apart from all such considerations the period 

 of the direct observations, and the possible 

 duration of the mutability through even more 

 than a century, would constitute only a moment, 

 if compared with the whole geologic time. 

 Starting from this conception the pedigree of 

 our mutations must be considered as only one 

 small group. Instead of figuring a fan of mu- 

 tants for each year, we must condense all the 

 succeeding swarms into one single fan, as might 

 be done also for Draha verna and other poly- 

 morphous species. In Oenothera the main stem 

 is prolonged upwards beyond the fan; in the 

 others the main stem is lacking or at least 

 undiscernible, but this feature manifestly is only 

 of secondary importance. We might even pre- 

 fer the image of a fan, adjusted laterally to 

 a stem, which itself is not interrupted by this 

 branch. 



On this principle two further considerations 

 are to be discussed. First the structure of the 



