Even When Nature Does Not Produce The Same Species In Analogous Climates, Either In The Plains Of Isothermal Parallels,* (We

May compare together either latitudes which in the same hemisphere present the same mean temperature (as, for instance, Pennsylvania and

The central part of France, Chile and the southern part of New Holland); or we may consider the relations that may exist between the vegetation of the two hemispheres under isothermal parallels.) or on table-lands, the temperature of which resembles that of places nearer the poles,* we still remark a striking resemblance of appearance and physiognomy in the vegetation of the most distant countries. (* The geography of plants comprises not merely an examination of the analogies observed in the same hemisphere; as between the vegetation of the Pyrenees and that of the Scandinavian plains; or between that of the Cordilleras of Peru and of the coasts of Chile. It also investigates the relations between the alpine plants of both hemispheres. It compares the vegetation of the Alleghanies and the Cordilleras of Mexico, with that of the mountains of Chile and Brazil. Bearing in mind that every isothermal line has an alpine branch (as, for instance, that which connects Upsala with a point in the Swiss Alps), the great problem of the analogy of vegetable forms may be defined as follows: 1st, examining in each hemisphere, and at the level of the coasts, the vegetation on the same isothermal line, especially near convex or concave summits; 2nd, comparing, with respect to the form of plants, on the same isothermal line north and south of the equator, the alpine branch with that traced in the plains; 3rd, comparing the vegetation on homonymous isothermal lines in the two hemispheres, either in the low regions, or in the alpine regions.) This phenomenon is one of the most curious in the history of organic forms.

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