The term pellis refers to the cellular cortical layers of a mushroom. The term was introduced by Dutch mycologist Cornelis Bas in 1969, who distinguished different layers of the pellis as suprapellis, mediopellis and subpellis.[1] He also distinguished various topographies of the pellis. For example, pileipellis refers to the cuticle of the mushroom pileus (or cap), while stipitipellis is the cuticle of the stipe (the stem).