Alice came across this fungi in her first adventure in Wonderland. The Caterpillar smoked his hookah upon it while asking Alice questions in short sentences that offended her. He revealed to her that one side would make her grow taller, and the other would make her smaller. When she bit one side of the mushroom, her torso shrunk and her head hit her feet. Eating it again however, made her neck extend so much that a pigeon mistook her for a serpent about to eat her eggs. Alice pocketed the mushroom pieces until she arrived back in the Great Hall of Doors where she nibbled from the mushroom piece again to shrink down to size.
American McGee's Alice
The Mushroom of Life was a toadstool that was guarded defensively by the Voracious Centipede, a very skilled insect fiend who knew combat well. Alice had to defeat him in order to eat a piece from the fungal growth, though very reluctantly as many toadstools were known to be toxic.
In Alice's Adventures in Wonderland, the right side of the mushroom made Alice shrink, and the left side made her grow. However, in American McGee's Alice, the right side made her grow.