The cells of this tissue are hard , very long and have thick walls. Tissue is protoplasm -free , lignin-containing, and is specifically for mechanical work. Although protoplasm is present in the initial stage, it decomposes very quickly and turns into a dead cell. Its cells are of two types . Namely: i) fiber , ii) scleroid. i. Fiber: They are very long , with thick walls and narrow ends. Depending on their location and structure, they have different names, such as : bustfiber , surfacefiber , xylem fiber. ii. Scleroids: These are also called stone cells. They are short , homogeneous , sometimes tall and sometimes stellar Their secondary wall is very hard , very thick and ligninous. Mature scleroid cells are usually dead. The cell wall is well-contained.