230 DAVIS— THE TEST OF A [April 23. 



certain new types. Thus from one of the species, CEnothera 

 stenomeres, a mutant gigas appeared with the diploid number of 

 chromosomes, and from another species, O. Reynoldsii, certain in- 

 dividuals throw from 60 per cent, to 80 per cent, of dwarfs. It is 

 too early to discuss the remarkable peculiarities of these forms since 

 the material of Bartlett has not yet been tested for its purity along 

 the lines presently to be discussed. Bartlett regards the new types 

 as " mutants " in the sense of De Vries. The important point for 

 our consideration at present is the fact that these wild plants ap- 

 parently continue to reproduce themselves from generation to gen- 

 eration even while giving rise to the new forms. 



With respect to the taxonomic status of the plants which we 

 have just considered the writer sees no alternative but their recogni- 

 tion as clear species. The Lamarckiana of De Vries, the biennis of 

 Linn^us, and most of the types which Bartlett has segregated from 

 the American wild Oenotheras breed true as to the mass of their 

 progeny. What further qualifications can taxonomy in reason de- 

 mand? Species they are by virtue of their morphology and by the 

 test of the experimental garden which shows their characters to be 

 stable to an extent that renders it certain that each line self-pol- 

 linated will maintain itself unchanged, indefinitely as far as we can 

 see, through successive generations. 



The argument that will follow as to the genetic constitution of 

 these species of CEnothera does not in the least affect the matter of 

 their recognition in taxonomy as species. It may be prefaced by 

 two questions stated as follows : Are the types pure species, homo- 

 zygous because the plants develop male gametes of one type only 

 and because their female gametes have a uniform germinal constitu- 

 tion ? Or, are the types heterozygous developing different types of 

 male gametes and different types of female; briefly expressed have 

 they in some degree a hybrid constitution? 



But it will at once be asked, how can a species be hybrid even 

 to a small degree and yet breed as true as do these forms under 

 consideration? Where in their behavior is evidence of a hybrid 

 constitution such as might appear in the splitting off of numerous 

 different forms varying from the parent type, some in small degrees 

 and some in larger degrees? Where is evidence of an orderly segre- 



