INTRODUCTORY EXPLANATIONS. 11 



would be the sjjecies appearing in all of them. Perhaps, 

 there is not a single native species, whose area is suffi- 

 ciently wide, and census sufficiently high in degree, as to 

 make it a native of every (iTu-al) parish. Probably two 

 hmidred species occur in eveiy comity ; although this is 

 stated only in conjectme. And the nmnber common to 

 England, Wales, and Scotland — unequal as these ancient 

 divisions are — may possibly amomit to eight hmidi-ed 

 species. 



The areas of species may be sufficiently shown by tra- 

 cing them through comities, or even much lai-ger sections of 

 Britain. To indicate their census iii a satisfactory manner, 

 it would be necessary to increase the lumiber of sections, 

 and thus make them include much smaller spaces singly. 

 For example, it may happen that two species ai'e foimd in 

 the same twenty counties each ; and, tested by coimties, 

 they would thus appeal* to have the same areas and same 

 census — which we wUl suppose expressed by the No. 

 ' XX.' Yet it might also happen, on subdividing the 

 twenty counties each into twenty sections, that one of the 

 two species is still found in all the lorn- hmidied sections, 

 while the other species appeal's in only one hmidied of 

 them. Their apparent census would thus vary according 

 to the test adopted, and must be expressed by the Nos. 

 ' 400 ' and ' 100 ;' or by ' XX, 400 ' and ' XX, 100.' 



To this supposed case there may be no exact pai'aUel in 

 natm'e ; although some approximation thereto might cer- 

 tainly be found. In the present work, as will shortly be 

 explained, the counties of Britain are grouped into eighteen 

 " provinces." Tonnentilla officinalis and Hypericum pul- 

 chiTim are found in eveiy province ; and it is not impro- 

 bable that they would equally be found in every county, if 

 looked for. But if we could subdivide all the counties into 

 sections of a squaie mile each, the Tonnentilla would 



