Mycorrhizal fungi. Hyphae (white) of a fungi (phylum Basidiomycetes) growing on the roots (brown) of the strawberry tree (Arbutus unedo). Mycorrhizal roots take up nutrients more efficiently than uninfected roots, while the fungi obtain carbohydrates and possibly B-group vitamins from the tree. The type of symbiosis (mutualism) seen here is known as an endotrophic mycorrhiza; the fungal hyphae form a mantle around the tree roots and also penetrate into the soil. In endotrophic mycorrhiza the fungus lives mainly within the cells of the root cortex.