491 



striking resemblance of appearance and physi- 

 ognomy in the vegetation of the most distant 

 countries. This phenomenon is one of the most 

 curious in the history of organic forms. I say 

 the history ; for in vain would reason forbid 

 man to form hypotheses on the origin of things; 

 he is not the less tormented with these insoluble 

 problems of the distribution of beings. 



A gramen * of Switzerland grows on the 

 granitic rocks of the Straits of Magellan. New 

 Holland contains above forty European phane- 

 rogamous plants ; and the greater number of 

 those plants, which are found equally in the 



mountains of Chili and Brazil. Remembering that every 

 isothermal line has an alpine branch (that, for instance, which 

 connects Upsal with a point in the Swiss Alps) the great 

 problem of the analogy of vegetable forms may be reduced 

 to the following expression ; 1st, to examine in each hemi- 

 sphere, and at the level of the coasts, the vegetation on the 

 same isothermal line, especially near convex or concave sum- 

 mits : 2d, to compare, with respect to the form of plants, on 

 the same isothermal line, to the north and south ?of the equa- 

 tor, the alpine branch with that traced iu the plains : 3d, to 

 compare the vegetation on homonimous isothermal lines in 

 the two hemispheres, either in the low regions, or in the al- 

 pine regions. 



* Phleum alpinum, examined by Mr. Brown. According 

 to the investigations of this great botanist, there can he no 

 doubt, that a certain number of plants are at once common to 

 both hemispheres. Potentilla anserina, prunella vulgaris, 

 scirpus mueronatus, and panicuin crus galli, grow in Ger- 

 many, in New Holland, and in Pennsylvania. 



