The Cycad species has the rare privilege of having survived at least 200 million years of the earth's history. Cycads apparently evolved from the Cycadofilicales ("seed ferns") late in the Pennsylvanian Period, about 300 million years ago. They were widespread during the Mesozoic era, some 65 to 225 million years ago, when the Dinosaurs were one of the dominant life forms. Judging from rarely found fossil cones it appears that cycads have changed relatively little in the last 100 million years which is why modern cycads are called "living fossils".Some cycads have a superficial resemblance to palms, others to ferns. The distinctive features of the plant are large, pineapple-like cones that protrude from the top of the stem and contain fleshy seeds. The plant's sex is determined by the cones, which are either pollen-bearing male, or seed-bearing female. This makes the Cycad a member of the more primitive gymnosperm family, also known as "naked seed" or "nonflowering seed" plants. They are pollinated by insects, not by wind as had been previously thought; their cones generate heat that vaporizes a sweet minty odor to attract insects to a supply of nectarlike liquid. The tallest cycad (Macrozamia hopei) on record was about 18 m (60 ft). Cycads are found today in tropical, subtropical and warm, temperate areas. There are more than 70 living species of cycads. Some species are locally abundant in Mexico, others are found only in western Cuba (where it is in danger of becoming extinct). The largest and most widely distributed genus is Zamia which ranges from the sandy woods of Florida and the West Indies through Central America and the Andes into Chile. Most African Cycad species, Encephalartos and Stangeria are found only in Southern Africa along the Southern Coastal regions of South Africa. Here the plant has a high profile due to extensive poaching from its natural habitat. In the Western Cape region a large collection of Cycads is held at the Kirstenbosch Botanical Gardens. In Australia, two genera, Macrozamia and Bowenia, are found only in New South Wales and Queensland. Cycas (about 15 species) is widely distributed ranging from Australia to the Pacific islands in the north and to India, China, Japan, and Madagascar.
[Index] [Introduction] [Goal] [Journey] [Portfolio] [The Cycad]
|Cycad Web Works Thu Jan 21 05:23:32 EST 2021
: # 203 : last modified 17/8/97 |
Cycad viewed by firstname.lastname@example.org