Amanita muscaria, the Fly Agaric or Soma (to some) metamorphosizes from the button to mature stage in 6 days. Detached from the ground, and although appearing larger, the mushroom does not gain additional mass. The button stage, although having no spores, is programmed genetically to evolve into a sporulating fruit body. Interesting!
*note that this mushroom re-orients itself to be horizontal, a response that is known as 'negative geotropism'. This response is common to most mushrooms which are connected to its mycelial mat. Once picked, some do; some do not.