I AM anxious to add a few further remarks on this interesting subject. It was during its investigation that I was so deeply impressed with the desperate struggle for existence which characterises the bordering fertile zones. I could there watch the contest on the very battle-field itself, and for that purpose I established myself for some months in the north of Uruguay, away from all other habitation, among the wooded banks and lagunes of the River Arapey. This river, though normally a quiet stream, is subject to tropical floods, during which the water rose often thirty feet in eight hours. The “monte,” or fertile wooded belt on each side, is intersected with ravines and lagunes teeming with animal and vegetable life of singular interest. The alligator, carpincho, myopotamus, nutria and other and numberless snakes thrive in the marshy swamps, while in the woods we met with the puma, the jaguar, the great lizard, the Podinama, the Nasua socialis, and numerous other singular animals and birds described in my little book. But it was among the flora that the principle of natural selection was most prominently displayed. In such a district, overrun with rodents and escaped cattle, subject to floods that carried away whole islands of botany, and especially to droughts that dried up the lakes, and almost the river itself, no ordinary plant could live, even on this rich and watered alluvial debris. The only plants that escaped the cattle were such as were either poisonous, or thorny, or resinous, or indestructibly tough. Hence we had only a great development of solanums, talas, acacias, euphorbias, and laurels. The buttercup is replaced by the little poisonous yellow oxalis with its viviparous buds, the passion-flowers, asclepiads, bignonias, convovuluses, and climbing leguminous plants escape both floods and cattle by climbing the highest trees and towering over head in floods of bloom. The groundplants are the portulacas, turneras, and œnotheras, bitter and ephemeral on the arid rock, and almost independent of any other moisture than the heavy dews. The pontederias, alismas, and plantago, with grasses and sedges, derive protection from the deep and brilliant pools; and though at first sight the “monte” doubtless impresses the traveller as a scene of the wildest confusion and ruin, yet, on closer examination, we found it far more remarkable as a manifestation of harmony and law and a striking example of the marvellous power which plants, like animals, possess of adapting themselves to the local peculiarities of their habitat, whether in the fertile shades of the luxurious “monte” or on the arid, parched-up plains of the treeless Pampas.