bord des routes pour deposer leurs excremens, dont on trouve des
monceaux dans ces endroits." Does this not partly explain the
circumstance? We thus have lines of richly manured land serving as
channels of communication across wide districts.
Near the Guardia we find the southern limit of two European plants, now
become extraordinarily common. The fennel in great profusion covers
the ditch-banks in the neighbourhood of Buenos Ayres, Monte Video, and
other towns. But the cardoon (Cynara cardunculus) has a far wider
range: [9] it occurs in these latitudes on both sides of the,
Cordillera, across the continent. I saw it in unfrequented spots in
Chile, Entre Rios, and Banda Oriental. In the latter country alone,
very many (probably several hundred) square miles are covered by one
mass of these prickly plants, and are impenetrable by man or beast.
Over the undulating plains, where these great beds occur, nothing else
can now live. Before their introduction, however, the surface must
have supported, as in other parts, a rank herbage. I doubt whether any
case is on record of an invasion on so grand a scale of one plant over
the aborigines. As I have already said, I nowhere saw the cardoon
south of the Salado; but it is probable that in proportion as that
country becomes inhabited, the cardoon will extend its limits. The
case is different with the giant thistle (with variegated leaves) of
the Pampas, for I met with it in the valley of the Sauce. According to
the principles so well laid down by Mr. Lyell, few countries have
undergone more remarkable changes, since the year 1535, when the first
colonist of La Plata landed with seventy-two horses. The countless
herds of horses, cattle, and sheep, not only have altered the whole
aspect of the vegetation, but they have almost banished the guanaco,
deer and ostrich. Numberless other changes must likewise have taken
place; the wild pig in some parts probably replaces the peccari; packs
of wild dogs may be heard howling on the wooded banks of the
less-frequented streams; and the common cat, altered into a large and
fierce animal, inhabits rocky hills. As M. d'Orbigny has remarked, the
increase in numbers of the carrion-vulture, since the introduction of
the domestic animals, must have been infinitely great; and we have
given reasons for believing that they have extended their southern
range. No doubt many plants, besides the cardoon and fennel, are
naturalized; thus the islands near the mouth of the Parana, are thickly
clothed with peach and orange trees, springing from seeds carried there
by the waters of the river.
113