Mr. U. 15. Iliutls on Geoyrapluc Botany, 19 



the other is extremely slight ; nor docs this increase as we ad- 

 vance to tlie south. To the north, on tlie contrary, there is u 

 gradual increase in the number of species occurring in the dif- 

 ferent divisions, and where the union of the land is great, many 

 of the species have wide ranges of growth. It is stated that of 

 the native flora of the United States, upwards of a seventh of the 

 phanerogamic plants are common to Europe, and still further to 

 the north the proportion is nuich greater. In the visits of Cap- 

 tain Bcechey to Kotzebue's Sound in the Blossom ship of war, 233 

 species were collected; ofthesell7,or as nearly one-half as is pos- 

 sible, are met with in the north of Europe. Hence it appears 

 that the large seas ha\e l)een barriers to the diffusion of the i)rc- 

 sent flora of the earth. 



3. In confirmation of the views just expressed, we will men- 

 tion some of the statements made by botanists respecting the 

 frequency with which species are repeated, or in other words, the 

 value of duplicates in those portions of the earth which have been 

 subject to their investigations. 



It is not unusual to meet with passages like the following in 

 the narratives of even the most distinguished navigators. The 

 author, the unfortunate La Perouse, is speaking of the vegetation 

 around Port de Fran9ais, in 58^ 37' N.L. : "Among these pot- 

 herbs we saw almost all that are common in the meadows and 

 mountains of France;" and again in the same page, " No vege- 

 table production of this country is unknown in Europe." The 

 latter part of this is so far from being the case, that on this coast, 

 and very near Port de Fran9ais, new species may still be dis- 

 covered. It is most true that the general character of the vege- 

 tation is strikingly like that of France, England, or the North of 

 Europe, and the traveller recognizes with much pleasure very si- 

 milar plants to what he has been accustomed to see in his own 

 country. But on a minute inspection, characters are discovered 

 which distinguish many of them from their Eiu-opcan represen- 

 tatives ; whence we learn the importance of accurate and skilful 

 observation in ascertaining what plants are to be considered as 

 distinct from, or identical with, those of another country. In 

 many instances this task is so difficult as to require all the judge- 

 ment and cx])erience of a practised botanist. It is only in the 

 writings of the most sagacious travellers that we can hope to find 

 that coiTcctness in details worthy of implicit confidence. 



The world may be divided into six sections, constituting so 

 many distinct provinces of the vegetable kingdom, and having 

 the watery barrier which separates them more or less complete. 

 Europe is the first of these, and the isolation is less than in any 

 of the others; Asia with its islands; Africa, including Madagas- 

 car and .some islands ; North Anuricj!, extending as far ^outh as 



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