Arum-type refers to the morphology of fungal hyphae living in, or around plant root cells. * Forms in arbuscular or tree-like fashion, branching off dichotomously at predetermined junctions. This is a type of mycorrhizal infection whereby the fungus in question invaginates the cell membrane of a plant cell, and branches in manner.Arum-type growth of hyphae is used in endomycorrhizal symbiosis with a plant. * Often, but not always, accompanied by hyphal growth.