What is the X in X-mas?
A specialized absorbing structure of a parasitic plant, such as the rootlike outgrowth of the dodder, that obtains food from a host plant. In parasitic fungi, haustoria are specialized hyphae that penetrate the cells of other organisms and absorb nutrients directly from them.
highly modified stem or root of a parasitic plant, such as mistletoe or dodder, or a specialized branch or tube originating from a hairlike filament (hypha) of a fungus. The haustorium penetrates the tissues of a host and absorbs nutrients and water.