The fruit body is the visible part of the growing fungus. It is supported by and develops from an extensive network of thread-like filaments called hyphae. Hyphae are often collectively termed the mycelium; the food-absorbing part of the fungus—as opposed to the spore-producing fruit body of the fungus—is called the vegetative mycelium. The individual hyphae that compose the mycelium absorb nutrients and water from the substratum in which they are growing. When the nutrient supply is adequate and environmental conditions are favorable, some fungi may grow in the same location for several years. Fungi cannot make their own food, namely carbohydrates, as can green plants. Some species are saprobic, obtaining nutrients from dead organic material, whereas others are parasitic on living plants or animals or even on other fungi. Many fungi, especially gilled mushroomes and boletes, have an extensive mycelium that lives in association with the roots of woody plants. This association, which is beneficial to both the fungus and host plant, is termed a mycorrhiza.