They generally grow very slowly and possess remarkable longevity, with some live specimens being as old as 1,000 years. Like the other gymnosperms, the cycads are ligneous plants, but the wood is spongy. The leaves are pinnate or pinnately- compound, with a heavy, ligneous base that generally persists on the trunk after the rest of the leaf falls. Leaflets can be directly opposed or alternating, toothed or smooth, and normally are quite rigid. Central vein marked and presence of lateral veins.
All cycads are dioecious, that is to say, separate male and female plants exist.
Instead of cones, female plants of Cycas species have megaesporophyls, which are modified leaves. Although scientifically they are plants of much interest because of their enormous antiquity, economically the have little food value. Sago is extracted from the caudex of some species, which is used as food in certain areas. The seeds of some species are also processed into an equally nutritious flour. Dioon edule Cycas revoluta Ceratozamia mexicana As much in the wild state as in culture, fertile seeds can only be formed when plants of different sexes grow near one another and their reproductive structures mature simultaneously.