600 Mutations 



which of course would have remained concealed 

 if its multiplication had been checked in the or- 

 dinary way. 



Many species have had occasion to invade new 

 regions and cover them with hundreds of thou- 

 sands of individuals. First are to be cited 

 those species which have been introduced from 

 America into Europe since the time of Colum- 

 bus, or from Europe into this country. Some of 

 them have become very common. In my own 

 country the evening-primroses and Canada flea- 

 bane or Erigeron canadensis are examples, and 

 many others could be given. They should be 

 expected to vary under these circumstances in 

 a larger degree. Have they done so? Mani- 

 festly they have not struck out useful new char- 

 acters that would enable their bearers to found 

 new elementary species. At least none have 

 been observed. But poor types might have 

 been produced, and periods of mutability might 

 have been gone through similar to that which is 

 now under observation for Lamarck's evening- 

 primrose in Holland. 



From this discussion we may infer that the 

 chances of discovering new mutating species are 

 great enough to justify the utmost efforts to 

 secure them. It is only necessary to observe 

 large numbers of plants, grown under circum- 

 stances which allow the best opportunities for 



