V. INEQUALITIES OF DISTEIBUTION. 439 



unfortunately for phyto-geograpMcal science, lie has too 

 usually learned also to despise and disregard these 

 "common things," in an acquired taste for rarities, more 

 fanciful than philosophical. To the pliyto- geographer, 

 however, the commonest plants can remain sources of 

 interest and objects of research, indii^ectly through their 

 localities and ranges, equally with the rarest kinds, in 

 searching for which botanical collectors evince so much 

 ardour. 



The thoughtful observer of nature takes longer and 

 deeper views. He seeks an answer to the question, 

 whether those inequalities of rarity and frequency, of 

 wide and restricted distribution, are simply fortui- 

 tous ? — whether they are related by causation or other- 

 wise to known differences in the present physical 

 geography of the island ? More than this, he may 

 extend his investigations so far as to seek out other and 

 remote explanations, drawn from ascertained facts and 

 probabilities in the past history of the earth, or of 

 Britain by itself ; with less remote explanations traceable 

 through the history of human operations within Britain. 

 The most advanced phyto- geographers yet stand only at 

 the site of some future edifice ; they are still at the 

 beginnings of such investigations, and they can see the ex- 

 planations only in a disjointed and very incomplete form. 

 Sufficient is seen, however, to warrant a belief that the 

 jn-esent distribution of plants is not accidental, but is the 

 result of past geographical or geological changes and 

 present adaptations. Chiefly of the latter ? 



It is true, several of the species now aj)pear dotted 

 about Britain in a manner which it seems very difficult 

 or impossible to account for. We are unable to say how the 

 plants got into their present localities, or why so many of 

 them remain there, year after year, century after century, 



