Along with the fleshy stem they may have contractile properties which serve to regulate the level of the stem in the ground. Specialised, upright-growing, branched roots, known as coralloid roots, are also produced by all species. These roots contain symbiotic blue-green algae which can fix nitrogen from the atmosphere. The stems of cycads may be completely subterranean or emerge from the ground and be trunk-like. Soil depth may influence this development and in shallow, stony soils, species which normally have subterranean stems may develop an above-ground trunk.
Cycads reproduce when mature by the production of cones.
A plant is either male or female and the cones of each sex are usually quite different in size and shape and to a much lesser extent colour. Specialised woody growths on the cones, called sporophylls, bear the sexual parts with those of the male cone producing pollen and on a female cone they bear large ovules which if fertilised develop into seeds.