light during the day and from the light during the night, like the shoots of any common plant; so that it is not easy to understand how they could have got under a trellis close to the wall. {184} _Root-climbers_.—A good many plants come under this class, and are excellent climbers. One of the most remarkable is the _Marcgravia umbellata_, the stem of which in the tropical forests of South America, as I hear from Mr. Spruce, grows in a curiously flattened manner against the trunks of trees; here and there it puts forth claspers (roots), which adhere to the trunk, and, if the latter be slender, completely embrace it. When this plant has climbed to the light, it produces free branches with rounded stems, clad with sharp-pointed leaves, wonderfully different in appearance from those borne by the stem as long as it remains adherent. This surprising difference in the leaves, I have also observed in a plant of _Marcgravia dubia_ in my hothouse. Root-climbers, as far as I have seen, namely, the Ivy (_Hedera heliæ_), _Ficus repens_, and _F. barbatus_, have no power of movement, not even from the light to the dark. As previously stated, the _Hoya carnosa_ (Asclepiadaceæ) is a spiral twiner, and likewise adheres by rootlets even to a flat wall. The tendril-bearing _Bignonia Tweedyana_ emits roots, which curve half round and adhere to thin sticks. The _Tecoma radicans_ (Bignoniaceæ), which is closely allied to many spontaneously revolving species, climbs by rootlets; nevertheless, its young shoots apparently move about more than can be accounted for by the varying action of the light.