I decided to try the Fungal Arts path, the first skill, called Mushrooms Farmer is described as
Mushroom Farmer: You collect molds, spores, and fungus. You like to grow mushrooms on the bodies of your enemies. Sometimes this comes in handy; usually it's just weird.
When I use that skill it creates spores: I tried eat them but I can't, I tried put on dead bodies, nothing happens. How to use them?
According to this forum post on the official forums it sounds like you have to plant the spores on either a dead enemy or a patch of dirt and wait a few turns.
... Simply you get a Rank1 ability to make 2 'Spore' items at Lv1, you take these spores, click on enemy corpses (or soil) wait 3-4 turns and they grow into Mushrooms, ...
It doesn't explicitly say how to do this, but implies you left-click place them on the relevant square (as with traps), and there's enough people there commenting on how useful the Mushroom Farmer tree is without correcting this statement, so I'd imagine it should be correct.
I've now tried this in-game, and it's simply a case of left-clicking on a corpse next to you with the spores held by the pointer. Wait a few turns and a mushroom will sprout.
BTW, the ability now automatically has a random chance to spawn a (random) mushroom from a slain foe. If you get a message that says "Sporification," then a mushroom will grow on that body in about three turns after that.
