These roots grow up out of the soil, rather than down into it, and are thus exposed to light which the cyanobacteria need. In return for providing this stable habitat, the cycad acquires nitrogen nutrients from the bacteria. Cycads grow in a number of tropical and subtropical climates. Though they are often among the larger plants in their environment, cycads are no longer abundant or dominant components of the world flora. Today's cycads are found on every continent except Europe and Antarctica, but are restricted to a limited number of areas in the tropics and subtropics.
Cycads grow in a number of different habitats.
Species may be found as components of the forest understory in both rainforests and seasonally dry forests, or occasionally as members of the forest canopy . Other cycads grow in loose stands in grasslands, forming a kind of savanna. Exceptional among the cycads are species of Encephalartos , one of which is visible at right, which grow in eastern Africa at very high elevation. Many cycads may be grown outdoors in California and the southern United States, but they cannot seem to tolerate the less equable climate in other parts of the nation. Many cycads face imminent extinction.