186 MR. BUNBURY ON THE VEGETATION OF BUENOS AYRES 



the great river, nothing is seen but tertiary formations of a very late date : first, the mud 

 and marl of the Pampas, and further south, the gravel and shingle of Patagonia. So 

 absolute is the fine of demarcation, that, while on the northern bank of the river the 

 granitic rock is perpetually showing itself on the surface in low rocks and hillocks, on 

 the south bank not a stone nor a pebble is to be found, and all the stone used at Buenos 

 Ayres, for paving and other purposes, is brought from across the river. But, notwith- 

 standing this remarkable difference in the geological structure of its two banks, the Plata 

 does not form a botanical boundary-line. There are indeed several species of plants 

 which are confined to one or the other side, and some families, principally tropical, which 

 do not cross it ; yet the leading characteristics of the vegetation, both as to its general 

 physiognomy and its prevailing forms, are the same on both sides. The whole country, 

 therefore, from the frontier of Brazil southward, as far as the Pampas vegetation extends 

 (or to the border of Patagonia), may be considered as one botanical province, which, for 

 the sake of convenience, I shall provisionally call the Argentine Region, from the name 

 of the great river. 



The botanical characteristics of this region are well marked. The most striking pecu- 

 liarity of its physiognomy is the almost entire absence of trees, and the scarcity even of 

 shrubs, except along the banks of the principal rivers. Every one who has come from 

 Bio de Janeiro to Monte Video and Buenos Ayres has been struck with the contrast 

 between the gigantic vegetation of Brazil, and the bare, treeless, almost barren character 

 of the shores of the Plata, where the cultivated poplars, and the flower-stems of the 

 Agave, and here and there a solitary Ombu tree (Phytolacca dioica), are the only objects 

 that relieve the nakedness of the country. Yet the vegetation along the river-side, at 

 least near Buenos Ayres, may almost be called luxuriant in comparison with that at a 

 short distance inland. It is not that the vegetable covering of the soil is really scanty or 

 meagre, but the vast majority of the plants which compose it are herbaceous, of low 

 growth, and for the most part not very conspicuous. This treeless character of the 

 country has been forcibly described, and its possible causes most ably discussed, by 

 Mr. Darwin, in his 'Journal.' The immediate banks of the Uruguay and the Parana, 

 however, and the islands in those rivers appear to be wooded, though not with trees of 

 great height or size. 



As compared with the vegetation of Brazil, that of the Argentine region is distinguished 

 not only by the predominance of herbaceous plants, but (as might be expected) by the 

 diminished numbers of tropical families, and also by something of a more European phy- 

 siognomy. I cannot, however, think that this resemblance of the Argentine to the Euro- 

 pean flora is as great as it has been represented by some celebrated botanists. The re- 

 semblance appears to me partly fallacious, occasioned by the abundance of naturalized 

 European plants ; and, excluding these, to consist rather in a certain general similarity 

 of outward appearance than in a real botanical analogy. 



Schouw, indeed, (as quoted by Meyen in his ' Geography of Plants,') says that, " out of 

 109 genera which belong to Buenos Ayres, 70 appear in Europe;" and St. Hilaire, a 

 very high authority, states that, of 500 species collected by him in the Banda Oriental, 

 between the mouth of the Plata and that of the Bio Negro, a tributary of the Uruguay, 



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