species are enabled to strike root and flourish under the most different climatic conditions. In spots where the land offers itself kindly and favourably they quickly bud, and attain to a breadth of propagation which narrows the area of the other flora of the district, and seems ever to push forward towards sole dominion. As though it were the sun of their home that ripened them, as though the juices of their far-off place of origin ran in them, they advance with prosperous development till the native growths are seized with fear at these ineradicable children of a foreign soil. Upon barren cliffs and in lonely abysses—where blossoming and sprouting seem impossible—they know the secret of existence; they surmount every obstacle, and twine themselves around their unwilling standing-places with insuperable strength, until the ramifications of their fibres, penetrating deeper and deeper into
