Know Your Mushrooms ** 1/2 (NR; 1:14): Most people could only name two things that mushrooms are good for: feeding your face or feeding your head. The documentary “Know Your Mushrooms,” screening this weekend at Webster University, delves into the tasty and trippy properties of humble fungi; but it also tells us much more. For instance, certain mushrooms are believed to shrink cancerous tumors, and mushrooms have be used to soak up oil in polluted waters.

Payful director Ron Mann (who’s done documentaries about comic books, marijuana, and hot rods) visits the late-summer Telluride Mushroom Festival in Colorado, where mycophiles enjoy mushroom cook-offs, hunting expeditions and lectures. We learn that fungi soak up organic debris in dark, moist environments–the largest living thing on earth is a forest-dwelling fungus in Oregon that measures more than three square miles–and we go into the Rockies with an expert collector.

The movie’s a bit coy about the real reason that many of the festival attendees collect mushrooms, but the truth takes effect after half an hour, about the time that the Flaming Lips’ soundtrack kicks in.  The costumed characters in the musical mushroom parade are sustaining a psychedelic tradition that dates back thousands of years. An academic opines that prehistoric hippies used mushrooms to improve their sensory perception–and thus their ability to survive–and others suggest that mushrooms may have colored the writing of “Alice in Wonderland” (believable) and the New Testament (dubious).

This short movie is not rigorous enough to convert those who aren’t already part of the mushroom cult, but it does whet the appetite.

(”Know Your Mushrooms”: screens Friday at 9 p.m. and Sunday at 8 p.m. in Moore Auditorium at Webster University. General admission is $6. Below are a couple morsels.)