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XX. Notes on the Vegetation of Buenos Ayres and the neighbouring districts. 

 By Charles James Pox Bunbury, Esq., F.B.S., F.L.S. 8fc. 



Read March 1, 15, and May 3, 1853. 



1 HE principal materials of the following notes are derived from the very extensive 

 botanical collections of the late Mr. Pox, formerly British Minister at Buenos Ayres, and 

 afterwards at Rio de Janeiro. The herbarium formed by Mr. Fox in the neighbourhood 

 of the former city, as well as at Monte Video, Maldonado, and other localities on the 

 northern shore of the Bio de la Plata, and along the lower part of the river Uruguay, 

 during the years 1831, 1832 and 1833, is so considerable, that I am inclined to think it 

 may be viewed as representing a great part of the vegetation of those countries, and may 

 afford sufficient ground for the remarks which I propose to make on its leading charac- 

 teristics. In a residence of about a month at Buenos Ayres, in the beginning of 1834, I 

 had myself the opportunity of becoming acquainted with the most prominent features 

 and general aspect of the vegetation. The principal published works from which I have 

 derived assistance, are M. Auguste de Saint Hilaire's Beport of his Travels in Southern 

 Brazil (published in the M^moires du Museum, vol. ix.), and the papers by Sir William 

 Hooker and Dr. "Walker- Arnott on the plants of Extra-tropical South America, in the 

 1 Botanical Miscellany ' and ' Journal of Botany.' I am indebted to Sir W. Hooker also 

 for very important assistance in naming the species contained in Mr. Pox's collection. 



The region of which I propose chiefly to treat, is that lying on both banks of the Bio 

 de la Plata, and on the lower part of the courses of the two great rivers by whose junc- 

 tion it is formed ; comprising consequently those parts of the republics of Buenos Ayres 

 and Banda Oriental which lie nearest to the Plata, between the parallels of 33° and 35° 

 S. lat. The collections before me were formed in the neighbourhood of the coast and of 

 the rivers, so that I am obliged to rely upon other authorities for the botanical cnarac- 

 teristics of the interior of those countries, in which, indeed, according to such information 

 as I can procure, a considerable degree of uniformity seems to prevail. I shall introduce 

 also some remarks on the vegetation of the southernmost part of Brazil, a district in 

 which Mr. Pox made large collections, and which forms a connecting link, botanically as 

 well as geographically, between the country I chiefly treat of, and the tropical parts of 

 the same continent. 



The Bio de la Plata, which, even as far up as Buenos Ayres, is between twenty and 

 thirty miles wide, forms a strongly marked geological boundary, separating two widely 

 extended and very dissimilar formations. All its northern shore is composed of crystal- 

 line rocks, — granite and gneiss, and their various modifications, — which range from thence 

 to the northward, uninterruptedly, through many degrees of latitude, constituting the 

 whole coast of Brazil to far within the tropic ; it is said, even to Bahia. On the south of 



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