340 DIFFERENCES OF ESTIMATE. 



botanical science, we can but affirm the number which cer- 

 tainly exceeds the sum of the vegetable species scattered over 

 the surface of our earth. To determine this total with mathe- 

 matical accuracy, we should need to have explored the 

 terrestrial crust, liquid and solid, land and water, from the 

 bed of ocean to the line of perpetual snow, and from the 

 equator to the poles. And as yet we are very far from having 

 obtained so complete a possession of the planet which has 

 been assigned as a dwelling-place to our poor humanity, 

 alas, more presumptuous than powerful I 



The number of plants mentioned by Theophrastus, Dios- 

 corides, and Pliny, whom we take to be the representatives 

 of ancient botany, does not exceed five hundred species. 

 How very few, compared with the presumable total! The 

 Middle Ages added scarcely anything to the botanical re- 

 searches of antiquity. It is only since the discovery of America 

 that we have seen the domain of Flora extending itself in 

 unexpected proportions. But we must come down to the 

 epoch of Linnaeus (the middle of the eighteenth century) 

 before we can obtain an accurate list of species, scientifically 

 classified. Murray's edition of the " Specilegium " of Linnaeus 

 contains two thousand and forty-two species, including the 

 Cryptogams. Wildmore, in another edition of the same great 

 work, raised the total to twenty thousand. And this was 

 the point at which our botanists had arrived when the nine- 

 teenth century opened. 



But it was not long before they perceived that all these 



