The inner layer of cortex is called endodermis. It is composed of single-layered and barrel-shaped cells. The cells are densely packed and without gaps. Suberin and lignin accumulate in the inner walls of the cells to form a ribbon-like lining. This is called the Caspian strip. It is named after the scientist Caspery (1865). Endothelial cells that have thin walls are called passage cells or passage cells. The endodermis of the stem of dicots (sunflowers) contains many starchy grains called starch sheath. Stems of monocots do not have endosperms.