Amanita muscaria (Fly Agaric)
Redwoods Regional Park, CA
This is perhaps the best known of the mushrooms outside of the ones in the store. This is the red version of Fly Agaric (the ones on the East coast are yellow). These are members of the most notorious family of mushrooms- the Amanitas. This one will make you pretty sick and cause you to sweat like crazy due to the muscaric acid it contains. People have been known to use these as hallucinogens, though its an incredibly bad idea. I really can't stress that enough.
