Says Li, there are about 25,000 orchid species around the world. Perhaps 3,000 of these have no leaves and do not photosynthesize, growing instead as tubers under the ground, only extending a flower stalk when it's time to bloom. These saprophytic orchids are symbiotic with fungi: the fungus enters the tuber to extract special nutrients, and the tuber gains nutrients from the dead fungus.
李家維指出，全世界蘭花約 2 萬 5,000 種，推估其中約有 3,000 種不長葉子、不行光合作用，而是以塊莖在地底成長，直到開花時才抽出花梗；這種腐生蘭與真菌共生在一起──真菌侵入球莖內取得特殊養分，蘭花球莖則藉殺死真菌換取成長養分。