The illustration below shows various stages in the development of a Deathcap mushroom.
Leftmost, is a very immature specimen, still within its all-enveloping universal veil. Next is a specimen where the stem has started to expand, thereby breaking the universal veil and in the third the stem has expanded enough to put the cap well above the soil. You can see the cup-like volva around the base of the stem. The volva is a remnant of the universal veil and you can see a small remnant left on the cap. Usually, no veil remain for long on the cap. In the final view the cap has expanded and there is the skirt-like ring or annulus hanging around the upper part of the stem. Before the cap expanded another membrane, the partial veil, extended from the stem to the cap margin and covered the gills. As the cap expands the partial veil breaks where it is attached to the cap margin and falls away to produce that 'skirt' around the stem.
Source: Some Colorado mushrooms, figure 14, by B.O. Longyear, published in 1914 by the Experiment Station at Fort Collins, Colorado.