INTRODUCTOEY OBSERVATIONS. 



summaries of details, adapted for comparison and re- 

 ference. 



A flora of 1500 species, real and nominal together, is 

 much too numerous for easy handling, or to allow of de- 

 scriptive details in comparing the vegetation of different 

 divisions of Britain, even considered by itself alone, apart 

 from the rest of the Earth. Suppose that it be sought to 

 compare descrij)tively the south with the north, the east 

 -with the west, the low grounds with the mountains, one 

 province with another, the relative frequency of the va- 

 rious species, the altitudes which they severally attain, 

 &c. &c. In attempting these and other such compari- 

 sons, by ordinary readable descriptions, the multitude of 

 names and objects would become embarrassing in a very 

 high degree. 



Any attempt to carry out corresponding comparisons 

 between the flora of the British Isles, as a whole, and the 

 floras of other parts of the World, would be quite futile 

 while only a small portion of a single volume could be 

 devoted to such an additional and more extended pur- 

 pose. And it has ah'eady been found, as was quite ex- 

 pected indeed, that a contraction into one or two volumes, 

 instead of an expansion into four volumes, would have 

 better suited the purses of those very few, among English 

 botanists, who seek anything more than a petty amateur 

 knowledge of individual species by name and sight. 



Nor would the subject of British geographical botany 

 be at all nearly exhausted under the two leading divisions 

 above mentioned, — the home and the foreign compari- 

 sons, &c. The flora of the whole Earth, as at present 

 distributed and known, is in itself a fragment only. The 

 flora of one island is a fragment of that present fragment. 

 That wliich is now seen, whether widely or locally, is the 

 result of countless changes in the past, now most imper- 



