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| Cycads are an ancient group of seed plants, sometimes called living fossils. They first appeared in Pennsylvania 300 million years ago. In the past, cycads attained a global distribution, extending over the earth from Alaska and Siberia to the Antarctic. Fossils are known from every continent. In addition to the eleven living genera, there are nineteen extinct cycad genera known only as fossils. Many cycads are facing possible extinction in the wild today, both because they live in endangered habitats such as tropical forests, and because they grow so slowly and reproduce so infrequently. |
 Cycas revoluta - Sago Palm Photo by: Andrew G. Seymour |
 Cycas circinalis - Emerging cones |
Commonly called Fern Palms, cycads are neither ferns nor palms but actually belong to the division of cone-bearing plants known as gymnosperms. The seeds of cycads are quite large, and are often brightly colored; red, purple, and yellow seeds are common. These colorful seeds are displayed as the cone matures and the seed bearing leaves separate from each other; the colors attract birds and a variety of mammals which disperse the seeds. Some cycads will produce heat or odors to attract animals. |
 Coralloid Roots Photo by: Andrew G. Seymour |
One of the more fascinating interactions among these plants is an association with a photosynthetic bacteria. In cycads, the cyanobacteria are sheltered in specially modified roots which have the appearance of coral, and are so called coralloid roots. 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 a stable habitat, the cycad acquires nitrogen nutrients from the bacteria. |
| The term gymnosperm comes from the greek words gymnos, meaning naked, and sperma, a seed. This name refers to the exposed nature of the seeds, which are not enclosed within a fruiting body, as are the seeds of flowering plants. There are four main divisions of gymnosperms with living representatives: the Conifers make up the largest and most significant division by far and are represented by pine trees, firs, spruces, and cedars among others; the Cycads; the Ginkgoes, which have unique fan-shaped leaves and seeds enclosed in a fleshy covering; and the Gnetophytes, whose wood contains vessels, a structural element typically found in flowering plants. |
 Cycas circinalis |
| The Welwitschia is a gnetophyte. This cone-bearing plant is the only one of its species and is confined to the temperate deserts of southwestern Africa. Since there is not much yearly rainfall, it is believed that the plant survives much of the time on fog and dew water absorbed through the surface of the leaves. Throughout the life of these plants, up to 100 years or more, they only produce two straplike leaves which become easily tattered and torn. The leaves have a meristem or growing point at the base which constantly add to the length of the leaves. Male and female cones are produced on separate plants, on stalks that emerge from the axils of the leaves so that they appear to be growing around the rim of the stem. Male cones bearing pollen are pictured in the upper left corner of this page. |
 Welwitschia mirabilis Photo by: Andrew G. Seymour |