Fungi

FUNGI. Fungi—sing. fungus; from the Greek sphongis (sponge)

Fungi are nonphotosynthetic and thus must absorb nutrients from organic matter formed by other organisms. The great majority of fungi obtain their food from dead organic matter, and hence are known as saprophytes; a relatively small percentage derive their food from other living organisms and are known as parasites. http://www.encyclopedia.com/topic/Fungi.aspx

More commonly known as Mushrooms or Toadstools, they appear mainly in autumn.  Each mushroom only lasts a short time, before rotting away into a decaying mess.  The most familiar of  Mushrooms have a stem, a cap and gills on the underside of the cap. Like little icebergs of the forest, only 10% of the mushroom is above ground.  The remaining 90% is an underground networth of microscopic threads spreading through the soil, feeding on dead organic matter.

While some are considered parasites, living on organic matter from the host,  they dont, unlike the common perception of parasites,  damage their host (as opposed to the Strangler Fig tree for example).