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 line 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 
Rio de Janeiro to Monte Video and Buenos Ayres has been struck with the contrast 
between the gigantie 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 Ombi 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 conspieuous. 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. | 
à "XD (as quoted by Meyen in his : Geography of Flants,’) says that, “out of 
ch 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 Rio Negro, a tributary of the Uruguay, 
