Abstract: There are three type cells infected by the mycorrhizal fungus, ArmiUaria mellea (Vahl ex Fr. ) Karst in the tube cortex of Gastrodia elata BI., namely the passage cells, host cells and digesting cells. Ultrastructural study demonstrated that the passage cells were distroyed by the hyphae, the host cells kept symbiotic with the hyphae, but the digesting cells could become inversely parasitic on the hyphae from which nutrient were being uptaken. The detail process of the digesting cells obtaining nutrient'from the fungus is described as follows: Firstly the digesting cells began to attack the invading hyphae by releasing numerious electron-transparent vesicles of lysosomal property, secondly they took up the soluble organic material leaked out from the digested hyphae by forming many electron-dense endocytic tubes and vesicles, and finally they endocytosed and hydrolysed the insoluble hyphal walls by forming large digesting vacuole in which a piece of hyphal wall was completely enveloped.

Key words: Saprophytic orchid, Gastrodia elata, Armillaria mellea, Nutrition, Endoeytosis