Yes Ken, these were often confused in identification with the magic mushroom as when dead and dried, as you can see from the picture, they look a lot like the top of a mushroom.
Doug,
"Talk about knowing the pedigree of a plant"
We cactophiles like as much details of the plant or where the seed was collected as possible. From the collection number we should be able to find out who originally collected the plant or seed and from which locality. The collection number is often more valuable on the plant than the name as you can always find all the details out from the collection number, including the name if it has one, but not from just the name itself.
There are thousands of collection numbers for cacti and I supplied many thousands I had already put on computer to help start Ralph Martin's collection numbers database which is available on the Internet for cactus collectors everywhere. If you scroll down the first link you will see he acknowledges this. This database is growing daily as more and more people supply their collection numbers and localities to it:-
http://ralph.cs.cf.ac.uk/cacti/fieldno.html
http://ralph.cs.cf.ac.uk/cacti/collector.html
I would not be surprised if other individuals were not running a similar facility for other groups of plants.
DaveW