Also, the viral image is of a generally nonpoisonous ... There are thousands of known mushroom species, but the medical reference website MedScape reports that about 100 species are responsible ...

While the "world's largest mushroom" may conjure up images of one single enormous spore, Armillaria ostoyae, or the honey mushroom, is actually a sprawling organism that covers acres of forest floor.

(Photo credit: RooM / Getty Images) There are more than a million estimated species of fungi. Mushrooms grow in a variety of colors and sizes. Edible mushrooms make up only a small fraction of fungi.