318 Plant Life and Evolution 



before they flower, this being notably the case with 

 many bulbous plants. 



Experiments with Alpines. Some very interest- 

 ing experiments have been made by Bonnier and 

 other students upon alpine plants, which illustrate 

 very clearly the hereditary character of changes in- 

 duced by altered environment. In some cases a 

 plant was divided into two portions, one being 

 grown at a low altitude, and the other transferred 

 to an alpine station, where it was grown for several 

 years. The latter in time developed the dwarf habit, 

 and several other characteristics of a true alpine 

 plant. After several years, these artificial alpines 

 were returned to the old environment, and it was 

 found that they gradually reverted to their original 

 form, and that the time necessary for this was ap- 

 proximately the same as that required to make the 

 change to the alpine type. It is a fair assumption 

 that a plant transferred to a new environment, and 

 subjected to this for a long period, would to all 

 intents and purposes thus become a new species, and 

 it is not likely that, if after a thousand years it 

 were returned to its old environment, it would ever 

 revert exactly to its original condition. 



It is probable that a critical study of plants 

 long naturalized in a new country would show marks 

 of constant change from the original type. It would 

 be interesting to know, for example, whether the 

 common European weeds that have been naturalized 

 in the United States for two or three hundred years, 



