As in other cell-walls, so here the older membranes may be altered by deposits of various substances, such as resin, calcium oxalate, colouring matters; or more profoundly altered throughout, or in definite layers, by lignification, suberization (Trametes, Daedalea), or swelling to a gelatinous mucilage (Tremella, Gymnosporangium), while cutinization of the outer layers is common.
From each of the four segments in the case of Tremella a long outgrowth arises which reaches to the surface of the hymenium From Strasburger's Lehrbuch der Bolanik, by permission of Gustav Fischer.
By the way, white fungus, also known as tremella, is a rubbery, jelly-like mushroom whose common name is Brown Witch's Butter.