It cannot have escaped the observation of the most inattentive, the tendencies which roots have generally to descend into the ground, and which stems have as commonly to grow upwards towards the sky; yet the very commonness of these things may have prevented their obtaining the attention that they merit; for it must be acknowledged, that to a mind directed to them they appear, however frequent their occurrence, not the less difficult to explain. It is sufficiently hard to comprehend why roots and stems should grow in different directions, the one downwards, and the other upwards; but when we add to these the constant manner in which the darker surface of a leaf is turned upwards, and the part of a flower painted with the most gorgeous colours is directed always towards the light, the subject becomes more interesting, and the more vexatious ought to be our ignorance: and, then, there are phenomena, produced by unusual circumstances, calculated to puzzle us still further, and increase our bewilderment. Such are the manner in which a geranium, growing at a window, bends its stems and leaves towards the glass; the manner in which a potato plant, growing in a cellar into which the light is admitted by a single chink, will acquire a most unusual height, and follow a most devious and uncommon track to reach that ray of which it appears enamoured; and the mode in which a root will descend, along the face of a bare rock, an extraordinary distance, in order to arrive at some spring or stream. These are objects well worthy of contemplation. A remarkable example of one of the facts just alluded to occurred many years ago in the tower of an old cathedral in England: a potato plant grew to the height of between thirty and forty feet, to get at the glimmering light of a partially closed window.