TYPES OF MUTATIONS AND THEIR POSSIBLE 

 SIGNIFICANCE IN EVOLUTION.^ 



DR. ALBERT F. BLAKESLEE 

 Statiox for Experimextal Evolution 



The beginning of the twentieth century saw the rise of 

 two concepts which have profoundly affected biological 

 thought and been of increasing influence in the trend of 

 experimental study of plants and animals. The mutation 

 theory of deVries based on the evening primrose, and the 

 laws of Mendel based on the garden pea, settled the date 

 of birth of the modern science of genetics. The studies 

 on these two plants have together formed a basis for 

 tlie main bulk of our present genetic investigations. 

 While the garden pea stands intimately associated with 

 a conception of inheritance of wider application than was 

 at first imagined, the evening primrose and the theory of 

 mutation connected with it are by many considered to 

 furnish an example of a valuable theory founded upon 

 incorrect interpretations. The belief is growing that 

 most of the new forms which ha\i" npjx'arcd in cultures 

 of the (Enotheras are not mutations at all and that the 

 evening primroses, as an abnoi-iiiai iiroup oi' phmts, arc 

 not to be seriously considered as rcpreseiitat ixc of the 

 processes of evolution in normal forms. 



In the short time at my disposal, I wish to outline some 

 recent findings in the jimson weed {Daiuya Stramonium) 

 whicli it is hoped may throw incidentally some lidit on the 

 more hlu'hlv involved pin'nonicna in the < l-:in>th.Tas. and 

 which nia.N M v^r a^ a ha-i^ of a hi-iof <liMMi^^i..n ot tli.'ir 



'I i!' : --i I- not supplied with a wide i-ange of 



oln ■Maraete,.. The ear!> Mudies of 



2rA 



