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Cycads in South Africa. Cycads / ˈ s aɪ k æ d z / are seed plants that typically have a stout and woody trunk with a crown of large, hard, stiff, evergreen and (usually) pinnate leaves. The species are dioecious, that is, individual plants of a species are either male or female. Cycads vary in size from having trunks only a few centimeters ...
Cycads all over the world are in decline, with four species on the brink of extinction and seven species have fewer than 100 plants left in the wild. [2] 23,420 species of vascular plant have been recorded in South Africa, making it the sixth most species-rich country in the world and the most species-rich country on the African continent.
Cycas is a genus of cycad, and the only genus in the family Cycadaceae with all other genera of cycad being divided between the Stangeriaceae and Zamiaceae families. Cycas circinalis, a species endemic to India, was the first cycad species to be described in western literature, and is the type species of the genus.
The sperm of members from the genus are large, as is typical of cycads, and Z. roezlii is an example; its sperm are approximately 0.4 mm long and can be seen by the unaided eye. [11] It was long believed that Zamia plants, like all cycads, relied completely on wind pollination.
While there are more than 200 species of cycads, only one is native to Florida, and only a couple are popular landscaping plants in our area.
The leaf-like character of Sporophylle gives Dioon a special position within the cycads. Dehgan & Dehgan described the genus as the most primitive of the cycads and suggested they put them into their own family. [15] A molecular genetic study of the chloroplast DNA revealed that it is at least the most primitive genus of neotropical cycads. [16]
Dioon edule, the chestnut dioon, is a cycad native to Mexico, also known as palma de la virgen. Cycads are among the oldest seed plants and even pre-date the dinosaurs. [3] It belongs to the Zamiaceae plant family within the order Cycadales.
During the Carboniferous, tree-like plants (such as Lepidodendron, Sigillaria, and other extinct genera of the order Lepidodendrales) formed huge forests that dominated the landscape. Unlike modern trees, leaves grew out of the entire surface of the trunk and branches, but fell off as the plant grew, leaving only a small cluster of leaves at ...