The Choice and Fixation of Variations 35 



the complex phenomena of the forms of organic life. For 

 a time, this philosophy was thought to be the one funda- 

 mental motive of the evolution or progression of life, but 

 we are n6w convinced that there are other motives or forces 

 at work; but it seems to be indisputable that natural 

 selection is a major force underlying the evolution of 

 plants, and it is the only one with which the person who 

 desires to breed plants need intimately concern himself. 



We must now determine what a variety is. This is a 

 vexed question, and one which seems never to be capable 

 of an answer that is satisfactory to the gardener. Time 

 and again, some person has introduced what he considered 

 to be a distinct new variety, only to find that other horticul- 

 turists dispute him and declare that it is only some old 

 variety renamed. And yet the introducer knows that 

 he has not renamed an old variety, but that he has propa- 

 gated a form which appeared or originated on his own 

 grounds. 



What is a variety? Now, let us see. Nature starts 

 out with the individual to make a new form. Every in- 

 dividual is unlike every other one. When the individual 

 differences are so well marked that we can readily de- 

 scribe and distinguish them, and so permanent that they 

 pass down nearly intact to a few generations, we say that 

 we have a variety. If the differences are still more 

 marked, we say that we have a species. Where the 

 variety ends and the species begins it may be utterly 

 impossible to determine ; and so we mark off at a certain 

 point and say, arbitrarily, that this much is variety and 

 that much is species. Asa Gray once said that " species 

 are judgments." Now, if there is no hard and fast line 



