ILLUSTRATIONS (13). EXTENT OF BOTANICAL SPECIES. 277 



1807, has described as many as 17,457 species of phanero- 

 gamia, reckoning from Monandria to Polygamia dicecia. If 

 to these we add 3000 species of cryptogamic plants, we 

 shall bring the number as given by Willdenow to 20,000. 

 More recent investigations have shown how far this estimate 

 of the species described, and of those preserved in herbariums, 

 falls short of the truth. Robert Brown* first enumerated 

 above 37,000 phanerogamia, and I at that time attempted to 

 describe the distribution of 44,000 species of phanerogamic 

 and cryptogamic plants, over the different portions of the 

 world already explored, f Decandolle finds, on comparing 

 Persoon's Enchiridium with his Universal System divided into 

 twelve families, that more than 56,000 species of plants may 

 be enumerated from the writings of botanists and European 

 herbariums.^ If we consider how many new species have 

 been described by travellers since that time, (my expedition 

 alone afforded 3600 of the 5800 collected species of equi- 

 noctial plants), and if we bear in mind that there are 

 assuredly upwards of 25,000 phanerogamic plants, cultivated 

 in all the different botanical gardens, we shall soon see 

 how much Decandolle's estimate is below the truth. From, 

 our complete ignorance of the interior of South America 

 (Mato-Grosso, Paraguay, the eastern declivity of the Andes, 

 Santa-Cruz de la Sierra, and all the countries lying between the 

 Orinoco, the Rio Negro, the Amazon, and Puruz), of Africa, of 

 Madagascar, and Borneo, and of Central and Eastern Asia, the 

 idea involuntarily presents itself to the mind that we are not 

 yet acquainted with one third, or probably even with one fifth 

 part of the plants existing on the earth. Drege has collected 

 7092 phanerogamic species in Southern Africa alone; and he 

 believes that the flora of that region consists of more than 1 1 ,000 

 phanerogamic species, seeing that in Germany and Switzer- 

 land, on an equal area (192,000 square miles,) Koch has 

 described only 3300, and Decandolle only 3645 phanerogamia 

 in France. 1 would here also instance the new genera, con- 

 sisting partly of high forest trees, which are still being dis- 

 covered in the neighbourhood of large commercial towns in 

 the lesser Antilles, although they have been visited by Euro- 

 peans for the last three hundred years. Such considerations, 



* General Remarks on the Botany of Terra Australia, p. 4. 

 + Humboldt, de distributione geographica Plantarum, p. 23. 

 Essai elementaire de Geographic botanique, p. 62. 



