The family is largely composed of plants that can tolerate acidic, infertile conditions. Like other stress-tolerant plants, many Ericaceae have mycorrhizal fungi to assist with extracting nutrients from infertile soils, as well as evergreen foliage to conserve absorbed nutrients. This trait is not found in the Clethraceae and Cyrillaceae, the two families most closely related to the Ericaceae. Most Ericaceae (excluding the Monotropoideae, and some Styphelioideae) form a distinctive accumulation of mycorrhizae, in which fungi grow in and around the roots and provide the plant with nutrients. The Pyroloideae are mixotrophic and gain sugars from the mycorrhizae, as well as nutrients.