plants that form mycorrhizae and obtain nutrient substances from the soil by means of the fungi that inhabit their roots. Most plant species are mycotrophic (except certain annuals, sedges, horsetails, club mosses, and aquatic plants). There are three groups of mycotrophic plants: plants that cannot develop from seeds without infestation of the fungus-symbiont (Orchidaceae); plants that can grow without a mycorrhiza but develop considerably better with parasitism by fungi (many trees, shrubs, and subshrubs); and plants that often have a mycorrhiza but develop equally as well without the fungus when nutritional conditions are favorable (linden, birch, many shrubs).