This district has been colonized by Europeans since the middle of the sixteenth century; but down to within a very few years ago immigration was on too limited a scale to make any very great change; and, speaking only of the pampean country, the conquered territory was a long, thinly-settled strip, purely pastoral, and the Indians, with their primitive mode of warfare, were able to keep back the invaders from the greater portion of their ancestral hunting-grounds. Not twenty years ago a ride of two hundred miles, starting from the capital city, Buenos Ayres, was enough to place one well beyond the furthest south-western frontier outpost. In 1879 the Argentine Government determined to rid the country of the aborigines, or, at all events, to break their hostile and predatory spirit once for all; with the result that the entire area of the grassy pampas, with a great portion of the sterile pampas and Patagonia, has been made available to the emigrant. There is no longer anything to deter the starvelings of the Old World from possessing themselves of this new land of promise, flowing, like Australia, with milk and tallow, if not with honey; any emasculated migrant from a Genoese or Neapolitan slum is now competent to "fight the wilderness" out there, with his eight-shilling fowling-piece and the implements of his trade. The barbarians no longer exist to frighten his soul with dreadful war cries; they have moved away to another more remote and shadowy region, called in their own language _Alhuemapu_, and not known to geographers. For the results so long and ardently wished for have swiftly followed on General Roca's military expedition; and the changes witnessed during the last decade on the pampas exceed in magnitude those which had been previously effected by three centuries of occupation. In view of this wave of change now rapidly sweeping away the old order, with whatever beauty and grace it possessed, it might not seem inopportune at the present moment to give a rapid sketch, from the field naturalist's point of view, of the great plain, as it existed before the agencies introduced by European colonists had done their work, and as it still exists in its remoter parts.