Like a mushroom, it lacks chlorophyll and is nonphotosynthetic. A mass of intertwined hyphae is collectively referred to as a mycelium. Under optimal conditions the hyphae often grow very rapidly, and it has been estimated that if all the hyphae produced in a day by a single soil fungus were laid end to end, they could extend for nearly a mile. Some mycorrhizal associations can be enormous, particularly in coniferous forest ecosystems. A single individual of Armillaria bulbosa has been discovered that permeates more than 30 acres of forest soil in northern Michigan and may be the world's largest living organism.
Some scientists speculate that it was spawned by a single spore thousands of years ago.
Another Armillaria in Washington was recently found to consist of a subterranean mycelial network with erect, above-ground mushrooms covering more than a thousand acres of forest soil. The aspen clone is connected by a common root system, and has literally climbed over mountains and across meadows. Any discussion of massive clonal colonies should also include the conjoined polyps of coral reefs. These fungus-like vessels produce the characteristic milky, latex sap of these two plant families. Pilostyles thurberi of the Colorado desert, live completely within the host and only emerge from their host to produce flowers.