ILLUSTRATIONS (23). THE ROSE. 321 



acliantifolia, and of the Cephalotaxus among the Taxineae, 

 vividly reminds us of the enigmatical and still obscure 

 conditions which determined the original distribution of 

 vegetable forms. This distribution can by no means be 

 satisfactorily explained either by the similarity or diversity of 

 the soil, by thermal relations, or by meteorological conditions. 

 I have long since directed attention to the fact, that the 

 southern hemisphere possesses, for instance, many plants of 

 the natural family of the Rosacea?, but not a single species of 

 the genus Rosa itself. Claude Gay informs us, that the Rosa 

 Chilensis, described by Meyen, is a variety that has become 

 wild of the Rosa centifolia, Linn., which has been naturalized 

 in Europe for thousands of years. Such wild-growing varieties 

 occupy large tracts in Chili near Valdivia and Qsorao.* 



In the whole tropical region of the northern hemisphere we 

 only found one single indigenous rose, our Rosa Montezuma?,, 

 ancl this was on the Mexican highland, near Moran, at a 

 height of 9336 feet. We may count among the strange 

 phenomena observed in the distribution of plants, the total 

 absence of the Agave from Chili, though it possesses Palms, 

 Pourretias, and many species of Cactus ; and although A. 

 americana flourishes luxuriantly in Roussillon, at Nice, at Bot- 

 zen, and in Istria, where it was probably introduced from the 

 New Continent since the sixteenth century, and where it forms 

 one connected line of vegetation from the north of Mexico, 

 across the isthmus of Panama, as far as Southern Peru. 

 With respect to the Calceolarias, I long believed that, like 

 the roses, they were only to be found exclusively on the 

 northern side of the equator. In fact, among the twenty-two 

 species that we brought w T ith us, not one was gathered to the 

 north of Quito and the volcano of Pichincha ; but my friend 

 Professor Kunth remarks that Calceolaria perfoliata, which 

 Boussingault and Capt. Kail found near Quito, advances also 

 as far as New Granada, and that this species, as well as 

 C. integrifolia, was sent by Mutis from Santa Fe de Bogota to 

 the great Linnaeus. 



The species of Pinus, which are so abundant in the wholly 



inter-tropical Antilles, as well as in the tropical mountain 



regions of Mexico, do not cross the isthmus of Panama, and 



are wholly wanting in the equally mountainous parts of iro* 



* Gay, Flora Chilensis, p. 340. 



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