Researchers in the US have found what is probably the largest living organism on Earth. It is a fungus that is growing through the earth and roots of trees in the Malheur National Forest in the Blue Mountains of eastern Oregon. Scientists say it covers 890 hectares (2,200 acres) of land - an area equivalent to about 1,220 football pitches. The fungus is called Armillaria ostoyae, but is more popularly known as the honey mushroom. This particular specimen is calculated to be about 2,400 years old, although it could be two to three times this age.