ECOLOGY PHOTOGRAPHIC         

CYCADS ARE PRIMITIVE GYMNOSPERMS that first appear in the geological record about 170 to 180 million years ago. They were present before the rise of dinosaurs and persist today in limited areas of the world. They can easily be distinguished from other gymnosperms by their compound leaves and palm-like growth habit. The sexes are separate and are pollinated primarily by wind.

These unusual plants are native primarily to Australia, eastern India and Malaysia, eastern and southern Africa, Madagascar, southern United States, Mexico, Central America and northeastern South America. Genera included in this group are: Bowenia, Ceratozamia, Chigua, Cycas, Dioon, Encephalartos, Lepidozamia, Macrozamia, Microcycas, Stangeria and Zamia, comprising about 220 species. The term cycad refers generally, and collectively, to all species of these 11 genera. In decline since the Jurassic Period, many are in ornamental or novelty cultivations.

The Cycadophyta (the cycads proper), comprise the three families Cycadaceae, Stangeriaceae, and Zamiaceae, with approximately 185 extant species in 11 genera. The group is recognized by the structure of its sporophylls, and by having pinnately compound leaves, though the genus Bowenia has doubly compound leaves, and some fossil forms have a simple leaf.

The extinct seed plant group Peltaspermales bears some resemblance to the cycads, and so has been suggested as their sister group. Others have suggested that the cycads may be closer relatives of the Medullosales, based on their similarity in growth pattern, mannoxylic wood, the presence of multiple leaf traces per leaf, and a double vascular system in the seeds. More recently, a fossil has been described with Ginkgo-like foliage but with cycad morphology and pollen structure, suggesting a possible relationship between two taxa that are otherwise quite unlike each other. The cycads' relationship to other living gymnosperms (especially the conifers) is still unclear.

The Bennettitales, another extinct group of seed plants which is sometimes called the Cycadeoids, was at one time classified in the Cycadophyta, but have since been found to be only superficially similar in their overall morphology -- their growth habit and leaf structure are similar to that of the cycads, but their reproductive organs suggest a closer relationship with the flowering plants.

Cycads are mostly endangered through habitat loss, but in recent years over-collecting has also become a concern. Mature or unique specimens can fetch astounding prices. Beyond their aesthetic value for the landscaping industry, they have little other economic impact. They were once used as foodstuffs, but that is no longer common because the seed coats and immature leaves contain carcinogens and neurotoxins. Some yield sago, a starch that is now largely in disfavor because of the carcinogens it contains. Where still used (primarily SE Asia and Indonesia), it takes the form of small whitish, pinkish, or brownish grains that are used in baking. Sago is exported to Europe and America, where it is used mainly for thickening soups and making puddings. In India it is boiled with sugar to make a jelly.

Kaffir bread of the Hottentots is made from seeds of Encephalartos. Seeds of Cycas and Zamia are also reported to be edible. Cycas leaves are dried, dyed and used for decoration.