Jurassic The Hunted

I didn't get all of the mushrooms the first time through because I missed that the achievement existed. As such, I had a lot to get. I tried just running through the first portion of Level 9 over and over by dying and either restarting the level or reloading the chapter. This didn't work. I had to actually play through to the end of the level to get enough mushrooms.

So you can't just keep dying / reloading the level to get to 50.