INTROD UCTION. 



in 1820, De Candolle calculated that at the least 

 56,000 species of plants were known. It was found 

 that the number of species preserved in the 

 Herbarium at the Jardin des Plantes was estimated 

 at the same figure, and that the collection of M. 

 Delessert contained as many as 86,000 species in 

 1847, although Dr. Lindley had estimated in 1835 

 that all the plants in the world might be included in 

 that number. 



Humboldt entered upon a series of calculations, 

 about this time, to show that all these estimates fell 

 short of the number which might be supposed to 

 exist. " Such considerations," he writes, " which 1 

 purpose developing more fully at the close of this 

 illustration, seem to verify the ancient myth of the 

 Zend-Avesta that the creating primeval force called 

 forth 120,000 vegetable forms from the sacred blood 

 of the bull." In 1845 Mr. R. B. Hinds estimated the 

 total of. phanerogamic and cryptogamic plants at 

 134,000 species. The next estimate we meet with 

 is in Henfrey (1857) at 213,000, but in 1855 De 

 Candolle had, by another process of reasoning, come 

 to the conclusion that the total could not be less 

 than 375,000 for flowering plants. Doubtless, these 

 calculations will go on increasing, as the highest is 

 found to be inadequate to represent even the whole 

 number of described species. At the present time 

 the very lowest estimate of authentic species of 



