252 Dafwin, and after Darwin. 



uniform standard of distinction whereby to draw 

 our boundary lines between varieties and species 

 on the one hand, or between species and genera on 

 the other. One or two quotations will be sufficient 

 to satisfy the general reader upon this point. 



Mr. Wallace himself alludes to " the great diffi- 

 culty that is felt by botanists in determining the 

 limits of species in many large genera,' and gives 

 as examples well-known instances where systematic 

 botanists of the highest eminence differ hopelessly 

 in their respective estimates of " specific characters." 

 Thus : — 



" Mr. Baker includes under a single species, Rosa canina, 

 no less than twenty-eight named varieties distinguished by 

 more or less constant characters, and often confined to special 

 localities, and to these are referred about seventy of the 

 species of British and continental botanists. Of the genus 

 Rubus or bramble, five British species are given in Bentham's 

 Handbook of British Flo?a, while in the fifth edition of 

 Babington's Manual of British Botany, published about the 

 same time, no less than forty-five species are described. Of 

 willows (Salix) the same two works enumerate fifteen and 

 thirty-one species respectively. The hawk weeds (Hieracium) 

 are equally puzzling, for while Mr. Bentham admits only seven 

 British species, Professor Babington describes no less than 

 seventy-two, besides several named varieties '." 



• 



Mr. Wallace goes on to quote further instances, 

 such as that of Draba verna. which Jordan has 

 found to present, in the south of France alone, no less 

 than fifty-two permanent varieties, which all " come 

 true from seed, and thus present all the character- 

 istics of a true species"; so that, "as the plant is 



' Darwinism, p. 77. 



