The volva is a membrane which envelops the entire plant in embryo, giving it the appearance of an egg. It originates at the base of the mushroom and furnishes it, during its foetal life, with the means of support and nourishment. Its texture is so delicate that it generally disappears, leaving very little trace of its existence on the adult plant. In many of the volvate species this organ exists only so long as they are under ground, and some mycologists restrict the term "volvati" to such only as retain it afterwards. As the young plant expands it breaks through the top of this volva or wrapper, and, emerging, carries with it patches of the membrane on the upper surface of the cap. These are more or less prominent, numerous, and thick, sometimes irregularly disposed, sometimes regularly in the form of plates, warts, etc. At the base of the stem of the mushroom the remains of the volva are seen in the form of a sort of wrapper. This is more or less ample, thick, and ascending. It is called free when it is loose or easily detached from the stem, and congenital when it cannot be separated from it without laceration. In some species it is distinctly membranous, and in others floccose, and friable in character, sometimes appearing in ridges as a mere border, at others broken up into scales, and, as the plant matures, wholly disappearing. The volva is a feature of great importance in the study of the Agaricini, of the subgenera Amanita, Volvaria, etc.