DOG-ROSE AND BRAMBLES. 133 



blackberries and dewberries. But in between them an 

 indefinite number of links exist, which can no more be 

 separated from one another than humanity could be 

 separated into three distinct groups of white-haired, 

 black-haired, and red-haired people. On the other 

 hand, the so-called blackberry bushes differ so much 

 among themselves in less conspicuous organs that they 

 have been sometimes divided into from six to forty 

 species, and sometimes lumped together again into one. 

 In the older days of natural science our Dryasdusts 

 fought fiercely with one another over these questions 

 of specific identity or difterence : nowadays, we are all 

 mostly agreed that such variations must naturally occur, 

 and that the attempt to reduce them all to artificial 

 symmetry is as impossible as it is futile. In some cases 

 species are well marked off from one another, because 

 natural selection has fixed steadily upon certain very 

 distinctive or highly important features, and has exag- 

 gerated those to an extreme degree : and then the inter- 

 mediate forms soon die out, because crossing becomes 

 impracticable, and the central stock has ceased to exist. 

 In other cases species merge imperceptibly into one 

 another: so that all one can do is to accept certain 

 approximate types as standards of reference, and con- 

 sider the intermediate forms as neutral specimens ; 

 because the central form still holds its own, and the 

 various lateral types, slightly favoured by natural selec- 

 tion in different directions, still remain capable of cross- 

 ing with one another — at least on their respective borders. 

 To this latter class such plants as the roses and the 

 brambles belong — as, indeed, do by far the larger 

 number of our native wild flowers. Indefinite variability 



