placed by the little poisonous yellow oxalis
with its viviparous buds; the passion-flowers, asclepiads, bignonias,
convolvuluses, and climbing leguminous plants escape both floods and
cattle by climbing the highest trees and towering overhead in a flood of
bloom. The ground plants are the portulacas, turneras, and cenotheras,
bitter and ephemeral, on the bare 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 luxuriant 'monte' or on the arid, parched-up
plains of the treeless pampas."

A curious example of the struggle between plants has been communicated
to me by Mr. John Ennis, a resident in New Zealand. The English
water-cress grows so luxuriantly in that country as to completely choke
up the rivers, sometimes leading to disastrous floods, and necessitating
great outlay to keep the stream open. But a natural remedy has now been
found in planting willows on the banks. The roots of these trees
penetrate the bed of the stream in every direction, and the water-cress,
unable to obtain the requisite amount of nourishment, gradually
disappears.

_Increase of Organisms in a Geometrical Ratio_.

The facts which have now been adduced, sufficiently prove that there is
a continual competition, and struggle, and war going on in nature, and
that each species of animal and plant affects many others in complex and
often unexpected ways. We will now proceed to show the fundamental cause
of this struggle, and to prove that it is ever acting over the whole
field of nature, and that no single species of animal or plant can
possibly escape from it. This results from the fact of the rapid
increase, in a geometrical ratio, of all the species of animals and
plants. In the lower orders this increase is especially rapid, a single
flesh-fly (Musca carnaria) producing 20,000 larvae, and these growing so
quickly that they reach their full size in five days; hence the great
Swedish naturalist, Linnaeus, asser