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XX. Notes on the Vegetation of Buenos Ayres and the neighbouring districts. 
By CHARLES JAMES Fox BUNBURY, Esq., F.R.S., F.L.S. $c. 
Read March 1, 15, and May 3, 1853. 
THE principal materials of the following notes are derived from the very extensive 
botanical collections of the late Mr. Fox, 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 Rio 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 Report of his Travels in Southern 
Brazil (published in the Mémoires du Muséum, vol. ix.), and the papers by Sir William 
Hooker and Dr. Walker-Arnott on the plants of Extra-tropical South America, in the 
* 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. Fox’s collection. 
The region of which I propose chiefly to treat, is that lying on both banks of the Rio 
. 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. Fox 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 Rio 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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