The information on which this question is based might not be totally correct... I'm looking for the name of a tropic fungus (or plant?) that lives high up in trees (as I remember correctly) and as a result doesn't get enough chlorine (or phosphorus, or fluorine), so it makes a noose to trap tiny worms and feeds on them. Anyone?

Found it! "Hunter fungi prey on tiny protozoa and worm-like creatures called nematodes. Some produce a sticky substance on their hyphae, which then act like flypaper, trapping passing prey. A species called Arthrobotrys dactyloides sets snares made out of loops formed by its hyphae. When a nematode comes into contact with the loops, the movement triggers the fungal cells to swell with fluid, constricting the loop like a noose around the hapless nematode. Other hyphae then grow toward the trapped prey, eventually punching through its body where they begin absorbing its fluids."