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Bark of ''Cycas rumphii''
'''Cycas''' is the type genus and the only genus currently recognised in the cycad family 'Cycadaceae'. About 95 species are currently accepted. The best-known species is ''Cycas revoluta'', widely cultivated under the name "Sago Palm" or "King Sago Palm" due to its palm-like appearance although it is not a true palm. The generic name comes from Greek ''kykas'' and means "palm tree".
A male cone of ''Cycas circinalis''
The genus is native to the Old World, with the species concentrated around the equatorial regions. It is native to eastern and southeastern Asia including the Philippines with 6 species (4 of which are endemic), eastern Africa (including Madagascar), northern Australia, Polynesia, and Micronesia. Australia has 26 species, while the Indo-Chinese area has about 30. The northernmost species (''C. revoluta'') is found at 31°N in southern Japan. The southernmost (''C. megacarpa'') is found at 26°S in southeast Queensland, Australia.
The plants are dioecious, and the family Cycadaceae is unique among the cycads in not forming seed cones on female plants, but rather a group of leaf-like structures each with seeds on the lower margins, and pollen cones on male individuals.
The caudex is cylindrical, surrounded by the persistent petiole base. Most species form distinct branched or unbranched trunks but in some species the main trunk can be subterranean with the leaf crown appearing to arise directly from the ground. The leaves are pinnate (or more rarely bipinnate) and arranged spirally, with thick and hard keratinose. The leaflets are articulated, have midrib but lack secondary veins. Megasporophylls are not gathered in cones.
Often considered a living fossil, the earliest fossils of the genus ''Cycas'' appear in the Cenozoic although ''Cycas''-like fossils that may belong to Cycadaceae extend well into the Mesozoic. ''Cycas'' is not closely related to other genera of cycads, and phylogenetic studies have shown that Cycadaceae is the sister-group to all other extant cycads.
Cycas is remarkable amongst the gymnosperms because of the following features:
It has the largest male cone and largest known sperms in plant kingdom.
The female cone is a false cone with megasporophylls loosely arranged on the main trunk.
The plant takes several years to grow,sexual reproduction takes place after 10 years of exclusive vegetative growth.
| Contents |
| Species |
| References and external links |
Species
References and external links
★ Cycad Pages: ''Cycas''
★ Singh, R., & Radha P. (2006). Cycas annaikalensis, A new species of Cycas from the Malabar Coast, Western Ghats, India. ''Brittonia'' 58 (2): 119-123.
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