In some trees the bark[1] is thin, as in the laurel and the lime; in others, again, it is thick, as in the robur; in some it is smooth, as in the apple and the fig, while in the robur and the palm it is rough: in all kinds it becomes more wrinkled when the tree is old. In some trees the bark bursts spontaneously, as in the vine for instance, while in others it falls off even, as we see in the apple and the arbutus. In the cork-tree and the poplar, the bark is substantial and fleshy; in the vine and the reed it is membraneous. In the cherry it is similar to the coats of the papyrus, while in the vine, the lime, and the fir, it is composed of numerous layers. In others, again, it is single, the fig and the reed for instance.