52o 



THE AMERICAN NATURALIST [Vol. L 



Before mutation studies had been extended to other 

 species of the genus from (E. Lamarckiana, Davis began 

 a series of experiments with the object of reproducing 

 the latter species as a hybrid of known origin. His first 

 experiments, involving (E. grandiflora as one parent, 

 were unsuccessful in producing a plant that bore more 

 than a superficial resemblance to (E. Lamar ckiana. Some 

 of the hybrids showed mutability, but none were obtained 

 which did not show obvious segregation in addition to 

 the mutability. Moreover, the mutations were not shown 

 to have been induced by hybridization, since none of the 

 parent strains were tested for constancy. As de Vries 

 suggested, the mutability was probably an inherited tend- 

 ency from one or both parents. 



Later hybrids, between (E. franciscana and (E. biennis, 

 were much more successful, in that they bore a much 

 closer resemblance to (E. Lamarckiana. The writer saw 

 hybrids last summer in Davis's garden that would surely 

 have been placed by any except the most ultra-critical 

 systematist under (E. Lamarckiana. They are being car- 

 ried into another generation, and the results will be looked 

 forward to with much interest. A true synthetic <E. La- 

 marckiana must show mutability, but must otherwise 

 come true from generation to generation. Moreover, it 

 must give twin hybrids in certain crosses with other spe- 

 cies. Even if Davis's later hybrids fulfill these condi- 

 tions, they will not demonstrate the origin of mutability 

 through hybridization, for one of the parents, (E. biennis, 

 has been shown by de Vries and Stomps to be a mutable 

 species, and the other, (E. f ranciscana, has not been tested. 

 To have much weight, an experiment such as Davis's 

 must show the origin of mutability de novo in a hybrid 

 from non-mutable parents. 



A more recent phase of the effort to prove (E. La- 

 marckiana a hybrid dates from the publication, in 1914, 

 of a paper by 0. Kenner. This author proposed a simple 

 Mendelian hypothesis to account for the twin hybrids and 

 high seed sterility of <E. Lamarckiana. It is well known 

 that in this species about half of the seeds are empty or 



