The stem is Lsolid and corky, much more solid than the flesh of the cap, and perfectly smooth, never being furnished with the slightest trace of a ring.
Both cuticularized and suberized membranes are insoluble in cuprammonia, and are colored yellow or brown in a soltition of chlor-iodide of zinc. It is probable that the corky or suberized cells do not contain any cellulose (Gilson, Wisselingh); whilst cuticularized cells are only modified in their outer layers, cellulose inner layers being still recognizable.
The leaf scar is protected by a corky change (suberization) in the walls of the exposed cells.
The potato tuber consists mainly of a mass of cells filled with starch and encircled by a thin corky rind.
Bast mats are now made chiefly in Russia, the bark being cut in long strips, when the liber is easily separable from the corky superficial layer.