it's a ground spawn(both underfoot mushroom and a strange dark fungus). no, kaladim constitutional is later in the game, however a strange dark fungus is supposed to spawn there as it is used in Thubr's Darkened Ale. This goes trivial at 102.
So I could be wrong if Thubr's was not classic, but I'm pretty sure they didn't add a useless drink later on? Maybe. Who knows with Sony.
But to wrap up and answer your question, yah ground spawns. Loc? Dunno. here's the directions for the spot:
Go into Kaladim, take the right path to zone into North Kaladim. Before you get to Everhot Forge theres a hidden path to the right with stone mushrooms in the ground. The underfoots and fungi are supposed to spawn in between these stone mushrooms. For other references, old school Alakazam can tell you a few things.
EDIT:
http://everquest.allakhazam.com/db/item.html?item=15321
i wont make you look when im asking for help.
i see the first posts were in 2003 on this fungi, however that does not denote the timeline as I stopped playing EQ in 2001 =P