Quote: Puffballs are ideal for beginning mushroomers because there are no poisonous species, and they're easy to tell apart from other groups if you pay attention. If a puffball has no stalk or "legs," and is pure white, soft, and undifferentiated (no separate parts) inside, then it's in an immature state, and it's a choice edible mushroom.
Puffballs beginning to turn yellow inside or are already forming powdery spores are too late to eat. But you may find them again in the same place the following year, when you can collect them when they're younger. (end quote) from the source:
http://www.wildmanstevebrill.com/Mus...0Overview.html