Cycads
Cycads
Cycads (/ˈsaɪkædz/; from the Greek kykás, a kind of palm tree) are seed plants with a long fossil history that were formerly more abundant and more diverse than they are today. They typically have a stout and woody (ligneous) trunk with a crown of large, hard and stiff, evergreen leaves. They usually have pinnate leaves.
Etymology
The word "cycad" is derived from the Greek kykás, which means "a kind of palm tree". The term was first used in English in the 19th century.
Description
Cycads vary in size from having trunks only a few centimeters to several meters tall. They typically grow very slowly and live very long, with some specimens known to be as much as 1,000 years old. Because of their superficial resemblance, they are sometimes mistaken for palms or ferns, but they are not closely related to either group.
Distribution
Cycads are found across much of the subtropical and tropical parts of the world. The greatest diversity occurs in South and Central America, where over 65 species occur. Some can survive in harsh desert or semi-desert climates (xerophytic), others in wet rain forest conditions, and some in both.
Classification
Cycads belong to the division Cycadophyta. They are divided into two families: the Cycadaceae and the Zamiaceae, which contain 10–11 genera and 306 species.
Reproduction
Cycads reproduce via seed. They are generally dioecious, therefore the male and female cones occur on separate plants.
Conservation
Many cycads, including all the species of Cycas, are listed as threatened or endangered.
Uses
Cycads have been used for food, medicine, and religious purposes by various peoples throughout history.
See also
References
External links
- Medical encyclopedia article on Cycads
- Wikipedia's article - Cycads
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