Here is a fantastic fungus. So much to say about fungi. Mushrooms are the surface fruit of a mycelium which is a mass of thread like hyphae. These organisms can be microscopic in size or huge- some are reckoned to cover thousands of acres (one single organism!).
 Scientists and ecologists are becoming ever more interested in the ways in which these networks of mycelia play a vital role in the health of the soil and the symbiotic (i.e. micorrhizal) relationships they have with plants. 
   Some mushrooms are deadly to humans, some are delicious, some are dangerous or edible depending on where they are found. Mushrooms are filters- if you pick an "edible" variety of mushroom by a motorway it will contain heavy metals; in an ancient woodland the same variety will be full of goodness. Indeed there is developing research into the use of funghi to process pollution. The book "Mycelium Running" by Paul Stamets is subtitled "How mushrooms can help save the world."
 And they look amazing. I was on a train heading southwards across London last week which stopped at Barnes station; glancing out the window I saw this superb specimen growing from a tree stump. Camera in hand I hopped off and lingered on the platform till the next train pulled in so I could commune with this magnificent mushroom.