xlii INTRODUCTION. 



levelling to obliterate those time-honoured 

 distinctions which were at least innocent, 

 even though the motive for them might 

 now be obsolete. Let us take an example. 

 The British Flora gives us four plants 

 under Achillea. That name has come 

 down from Dioscorides, and there is no 

 doubt that he and his successors generally 

 meant by that name preeminently the 

 familiar plant which we call Yarrow. 

 That plant was, and let me add still is, 

 with justice the object of a particular 

 attention. In the modern system four 

 species come under Achillea. But the old 

 prerogative of the Yarrow is not oblite- 

 rated by this circumstance. Whereas three 

 of the species have trivial badges, to wit, 

 A. ptarmica, A. serrata, A. tomentosa, 

 the Yarrow is designated Achillea Mille- 

 folium. Now Millefolium is an old synonym 

 which, though not so venerable a name as 

 Achillea, is yet of great antiquity; being 

 the term by which the plant had been for 

 ages known in the drug shops. Thus 

 then the most celebrated of the four species, 

 the typical plant of the genus, and that 





