2 INTRODUCTORY EXPLANATIONS. 



of facts, it is earnestly recommended that competent bo- 

 tanists will either make public through the periodicals, or 

 communicate to the Author, any infoiination which may 

 tend to fill up deficiencies, to remedy defects, or to correct 

 eiTors in either of the two earlier volumes. The third 

 volume, in which any such corrections &c. can be made, 

 will probably be prepared for the press in 1850 or 1851. 



With a view to save readers the trouble of back reference 

 to the former volume, while using this present one, it has 

 been deemed desirable to repeat tJie smaller diagram and 

 map, which were designed to show the geographical posi- 

 tion and comparative elevation of the "Provinces," or 

 groups of counties, indicated by the numeral figures in the 

 line which exhibits the " Area " of each species. 



Provinces. 



1. Peninsula. 



2. Channel. 



3. Thames. 



4. Ouse. 



5. Severn. 



6. S. Wales. 



Altitude of Provinces. 



7. N. Wales. 



8. Trent. 



9. Mersey. 



10. Humber. 



11. Tyne. 



12. Lakes. 



13. W. Lowlands. 



14. E. Lowlands. 



15. E. Highlands. 



16. W. Highlands. 



17. N. Highlands. 



18. N. Isles. 



