IV. PHYSICAL GEOGRAPHY. 133 



for pliyto-geograpliical purposes, when comparisons be- 

 tween small local floras are required. All being formed 

 on the same principle, in regard to the disputed topics of 

 native and alien species, of varieties and true species, &c., 

 they become more strictly comparable than the like num- 

 ber of local lists made out by different botanists, whose 

 views might differ widely in respect to such matters. The 

 varying width of Britain, and other geographical condi- 

 tions, caused the provincial areas to be stiU unequal, 

 though far less unequal than those of the counties. And 

 in this respect they are not equally comparable in respect 

 to their floras. 



Advancing knowledge has subsequently given facility 

 for subdividing the 18 provinces into more equal and 

 more numerous sections. For some purposes these 

 secondary or sub-provinces will be found more service- 

 able in use than the larger and fewer provinces. They 

 amount to 38 in number, and were explained on pages 

 324 to 328 of volume third. Their greater equality was 

 obtained by keeping the smaller provinces unchanged, 

 and subdividing the larger into two or three subordinate 

 sections. The rule of adhering to comital boundaries 

 was still observed in the sub-provinces, except that the 

 single county of York was subdivided into the two pro- 

 vinces of East Humber and West Humber. Subpro- 

 vincial lists of species might now be made out almost as 

 complete as the provincial lists were at the date when the 

 first volume of this work was written. Those for which the 

 Author's lists of species seem to be least complete, are the 

 Upper North Highlands, South-east Wales, South-west 

 Lowlands, Inner West Highlands, Ebudes, — nearly in the 

 order here enumerated. The dimensions or areas of the 

 provinces and subprovinces may be thus given in squai-e 



