Mycorrhiza (mī′ kŏr-rī′ zȧ), (in plants). The name means root-fungus, and refers to the fact that there exists an intimate association between certain fungi of the soil and the roots of higher plants, as orchids, heaths, oaks and their allies. The delicate mycelial threads of the fungus spread through the soil, enwrap the rootlets with a mesh of threads, and penetrate into the cells. By this means the fungus obtains food from the rootlet as a parasite. But it is also thought that the fungus threads spreading through the soil are of great service to the host-plants in aiding their rootlets in absorbing. If this be true, there is a mutual advantage in the association, for the small amount of nourishment taken up by the fungus is more than repaid by its assistance in absorption. See Mutualism.
