The Pampean landscape is doubtless one of the most uniform in the world. Its monotony is tiring to the eye; it is partly responsible for the mediocrity of most of the descriptions of the Pampas. But this uniformity is an advantage for the purpose of colonization. Attention has often been drawn to the rapidity with which plants and animals introduced by Europeans spread in the Buenos Aires district, and, pushing ahead of the breeders and farmers, colonized the Pampas. In the second half of the nineteenth century, when the whole extent of the plain beyond the ancient Indian frontier was occupied, the development of it was so much easier because it was possible to use simpler and more uniform methods of exploitation. It needed neither large capital nor long personal experience on the part of the immigrant. Basques and Italians who had only just landed could take an active part in it almost without apprenticeship. The primitive groups of population could advance from one zone of the plain to another and take with them their own methods of farming and breeding, their own form of rural economy. A close study will, however, enable us to detect appreciable physical differences in the Pampean plain. Neither climate nor soil is the same all over it. The name "Pampa" chiefly means a vegetal growth, a prairie. Its limits are the frontier of the scrub (_monte_), and strange as it may seem, it is still difficult to trace them exactly. North of Santa Fe, between the Salado and the Parana, the Pampa stretches as far as Fives-Lille, a little beyond 30 deg. S. lat.[76] On the Central Norte and the Central Argentine lines the fringe of the _monte_ reaches to Fuertin Inca and Malbran, about 170 miles north-west of Santa Fe. It then turns south-east and south, passing round the entire depression of Los Porongos and Mar Chiquita; and the line from Santa Fe to Cordoba crosses it at Francia and approaches the Rio Secundo. South of the Rio Secundo it goes westward and joins the foot of the Sierra de Cordoba south of the Rio Tercero (at the stream Tequia). From this point to La Cambre, some sixteen miles east of San Luis, the prairie extends as far as the edge of the sierras, and penetrates into the southern half of the Conlara depression, between the hills of Cordoba and of San Luis (Pampa de Naschel). The mimosa forest enters the steppe in narrow belts along the Rio Quinto to within a few leagues below Villa Mercedes, along the Rio Tercero as far as the confluence of the Saladillo, and along the Salado to the south of Santa Fe. There are, in addition, many isolated clumps of _chanares_ and more extensive patches of wood in the north-west corner of the prairie (Santa Fe province). The _monte_ along the Salado is continued south of Santa Fe along the Parana, as far as the point where the chief arm of the river reaches the cliffs on the right bank, at San Lorenzo. This is the domain of the _ombu_, a