[və¦sik·yə·lər är¦bəs·kyə·lər ‚mī·kə‚rīz·əl ′fən‚jī] (mycology) Mycorrhizal fungi that grow into the root cortex of the host plant and penetrate root cells to form two kinds of specialized structures, arbuscules and vesicles. Also known as arbuscular mycorrhizae.