No. 577] MUTATION THEORY OF BE VRIES 21 



Conclusions 



1. The Onagraceas are largely characterized by hybrid 

 contamination in na+ure. 



2. This statement holds with particular force for 

 Oenothera lamarckiana and other species of the genus 

 Oenothera, which have served as the most important basis 

 of the mutation hypothesis of De Vries. 



3. Constant hybrids or crypthybrids are of very com- 

 mon occurrence among the Angiosperms and have been 

 illustrated in the present article by reference to the gene- 

 tical conditions occurring in certain Kosaceae. 



4. The species of Oenothera are to a large extent, if not 

 wholly, crypthybrids. 



5. The objection raised by Bateson to the genetical 

 purity of Oenothera lamarckiana is confirmed and is ex- 

 tended to the Onagraceae in a general way, as well as to 

 other species of (Enothera. 



6. Hybridism is the best explanation yet put forward of 

 the peculiar conduct of (Enothera lamarckiana, as well as 

 other species of the genus in cultures. 



7. The mutation hypothesis of De Vries, so far as it is 

 supported by the case of (Enothera lamarckiana, is 

 invalidated. 



