Structural characteristics of leaf cells of Osmunda japonica Thunb.

1. epidermis: a layer of primary protective tissue on the surface of leaves, usually divided into upper epidermis and lower epidermis. The upper epidermis is located on the ventral surface and the lower epidermis is located on the dorsal surface. Epidermal cells are flat and closely arranged, usually without chloroplasts and usually with cuticles outside. Some epidermal cells often differentiate to form stomata or protrude outward to form trichomes.

2. mesophyll: assimilated parenchyma in epidermis, which usually has the following two kinds.

(1) palisade tissue: directly below the upper epidermis, the cells are usually 1 to several layers, long cylindrical, perpendicular to the epidermal cells, closely arranged in a grid, containing more chloroplasts. On two-sided leaves or needle-shaped leaves, palisade tissue is also distributed above the lower epidermis or around the whole inner epidermis, but there are also some aquatic and shade plants with no palisade tissue at all.

(2) Sponge tissue: The cells are irregular in shape and contain less chloroplasts. They are located under the fence organization, with unclear levels and loose arrangement, and look like sponges.

3. Veins are vascular bundles that run through mesophyll. The vascular bundles of the main vein are thicker, while those of the lateral veins and venules are smaller, usually with limited external toughness with xylem at the top and less double toughness with xylem at the middle. Vascular bundle is mainly surrounded by parenchyma, and when it is close to epidermis, it often has thick horny tissue or thick-walled tissue.

These tissues usually have more prominent parts below the main vein and are particularly developed. Calcium oxalate crystals are very common in leaf tissues and have various shapes according to plant species.