New Species of Oenothera 517 



systematic affinities at large. Many authors 

 have tried to solve it on the ground of compara- 

 tive studies and of speculations upon tlie bio- 

 logic relations of plants and animals. But in 

 vain. Contradiction and doubt still reign su- 

 preme. All our hopes now rest on the result of 

 experiments. 



Unfortunately such experiments seemed sim- 

 ply impossible a few years ago. What is to 

 guide us in the choice of the material? The 

 answer may only be expected from a consid- 

 eration of elementary species. For it is obvious 

 that they only can be observed to originate, and 

 that the systematic species, because they are 

 only artificial groups of lower unities, can never 

 become the subject of successful experimental 

 inquiry. 



In previous lectures we tried to clear up the 

 differences existing between nearly related ele- 

 mentary species. We have seen that they af- 

 fect all of the attributes of the plants, each of 

 them changing in some measure all of the or- 

 gans. Nevertheless they were due to distinct 

 unities and of the lowest possible degree. Such 

 unit-steps may therefore be expected to become 

 visible some time or other by artificial means. 

 On the other hand, mutations as a rule make 

 their appearance in groups, and there are many 

 systematic species which on close inspection 



