石细胞 lumen primary cell wall and middle lamella secondary cell all impregnated with lignin pit canal
石细胞
纤维 fibers Figure 4.5 Fibers. A. A cross section of a portion of stem tissue from a linden tree (Tilia sp ) x1, 000. Note the thickness of the walls of the darker fibers. B. A longitudinal section through fibers in a Welwitschia leaf, x1, 000 (B Photomicrograph by G S Ellmore)
纤维