2. Bark is the outermost part of woody plants, such as stems and roots of trees. Bark in a narrow sense includes cork, cork cambium and cork inner layer, as well as various dead tissues outside, and bark in a broad sense also includes phloem. The bark of some plants contains various alkaloids, tannins, dyes and spices, which can be used to extract various medicinal materials, drugs, poisons, resins and so on. Some kinds of bark can also be used to make cork, rope, weaving, making bark boats, drawing bark paintings and so on. , or directly used as decoration.