It surprised me that some people can still think that they spring out of the ground fully formed. There is far too much evidence against that idea for it to stand! I've witnessed it myself. Just look at my avatar. the big morel on the right was about half of that size when I first found it. But it seemed unique. It was late in the season, and the undergrowth was getting pretty high. It just "glowed" golden in that high, green grass. And when I touched my fingertips to it, it felt so cool and fresh!
So, I left it and came back 3-4 days later, and that morel had doubled in size. And the mushroom to its left, that was not in evidence before, had sprouted and grown to that size! As I said, it was late May, and there wasn't much season left, so I took them. Those 4 shrooms are what I found that day.