Retrograde Varieties 127 



they are evidently derived from it and limited 

 to it. And this is so true that nobody claims 

 the grade of elementary species for white roses 

 or white brambles, but everyone recognizes that 

 forms diverging from the nearest species by 

 a single character only, are to be regarded as 

 varieties. ^ 



This general conviction is the basis on which 

 we may build up a more sharply defined distinc- 

 tion between elementary species and varieties. 

 It is an old rule in systematic botany, that no 

 form is to be constituted a species upon the 

 basis of a single character. All authors agree 

 on this point; specific differences are derived 

 from the totality of the attributes, not from one 

 organ or one quality. This rule is intimately 

 connected with the idea that varieties are de- 

 rived from species. The species is the typical, 

 really existing, form from which the variety has 

 originated by a definite change. In enumer- 

 ating the different forms the species is distin- 

 guished by the term of genuine or typical, often 

 only indicated as a or the first; then fol- 

 low the varieties sometimes in order of their 

 degree of difference, sometimes simply in alpha- 

 betical order. In the case of elementary species 

 there is no real type; no one of them predom- 

 inates because all are considered to be equal in 

 rank, and the systematic species to which they 



