The following species are not described here. Interested readers are referred to the excellent descriptions provided by The Cycad Pages for data on all species of Cycas

C. armstrongii, C. baguanheensis, C. basaltica, C. brunnea, C. cairnsiana, C. chamberlainii, C. chevalieri, C. conferta, C. couttsiana, C. dilatata, C. gracilis, C. guizhouensis, C. hainanensis, C. immersa, C. inermis, C. jenkinsiana, C. kennedyana, C. lane-poolei, C. macrocarpa, C. megacarpa, C. micholitzii, C. normanbyana, C. ophiolitica, C. panzhihuaensis, C. papuana, C. pectinata, C. platyphylla, C. pruinosa, C. riuminiana, C. scratchleyana, C. siamensis, C. silvestris, C. szechuanensis, C. thouarsii, C. undulata, C. wadei.

map
Distribution of Cycas (1).

Cycas Linnaeus

Common Names

Cycads, Chinese name [Chinese].

Taxonomic notes

The number of species in the genus is uncertain; there has been no comprehensive generic study. Refer to The Cycad Pages for a current listing. There are probably about 40 species, most with very local distribution (1).

Description

Cycas is readily recognized by the leaflets, which have a prominent midrib and lack any obvious secondary veins. Other features useful in recognizing members of the genus include:
  • a subterreanean or emergent trunk clothed with persistent leaf bases
  • young parts hairy
  • new leaves not coiled but the leaflets coiled like watchsprings
  • leaflets not articulate at the base; lower leaflets abruptly reduced to a lateral series of paired, short, rigid thorn-like processes
  • male sporophylls arranged in a cone
  • female sporophylls arranged in a loose crown surrounding the vegetative apex of the stem
  • female sporophylls consisting of a linear stalk and an expanded apical lobe
  • female sporophylls usually bearing more than two ovules.

Trunk ovoid and subterreanean or slender to stout and emergent. Leaf bases retained on the trunk at senescence. New leaves erect with circinnate leaflets, emerging singly or in flushes, glabrous or with hairs that are shed with age. Mature leaves pinnate, oblong in outline, flat or V-shaped in cross-section, the older leaves spreading or deflexing after a flush in growth. Cataphylls prominent, arising in alternating flushes with the leaves, often rigid and pungent-tipped. Petioles swollen and hairy at the base, often with a lateral series of short, rigid, thorn-like processes borne more or less in opposite pairs, these being reduced lower leaflets. Rhachis lacking prickles, not twisted, straight or recurved in profile. Leaflets decurrent at the base, alternate to nearly opposite, with a prominent midrib, mostly evenly spaced except for the lower leaflets, straight or falcate, margins usually entire, sometimes serrulate in the distal third, lacking a callous base. Cones markedly dissimilar in shape and size. Male cones cylindrical; sporophylls arranged in a typical cone. Female cones loose and open; sporophylls arranged in a loose grouping surrounding the vegetative apex of the stem, with a linear stalk and an expanded apical lobe which may be entire, pinnatifid or deeply lobed on the margins. Ovules two to eight (rarely one) on each sporophyll, attached to the linear portion. Seeds platyspermic, ovoid to oblate, or rounded, the sarcotesta not usually brightly colored but bright red in C. taiwaniana (1).

Range

Southeast Asia, southern China, Malaysia, tropical Australia, Oceania, Japan, Africa, and Madagascar. Habitats vary widely, from coastal and near-coastal lowlands to interior hills and ranges. Many species grow in woodlands, a few in grasslands, and many on rocky slopes and escarpments where vegetation is sparse. Some are in areas with frequent wildfire. Some species, in arid regions, are deciduous during the dry season. Others, in coastal locales, have floating seeds that have given them a wide distribution (1).

Big Tree

Cycas angulata (heights to 12 m, diameters to 40 cm) and Cycas thouarsii (heights to 10 m, diameters to 45 cm) have the greatest height and diameter to be found in the genus.

Oldest

Dendrochronology

Ethnobotany

See Cycadales for general notes and see species descriptions for specifics.

Observations

Remarks

Generic name derived from the Greek koikas, apparently used by Theophratus for a type of palm. This was transliterated to kykas and thence to Cycas.

Cycas is viewed as the most primitive cycad genus (lower Permian of China). One fossil species has been described from the Eocene of Kyushu, Japan (1).

Citations

(1) Jones 1993.

See also: species descriptions at the Palm and Cycad Societies of Australia home page.

[Cycas] [Cycadaceae] [home]

This page is from the Gymnosperm Database
URL: http://www.geocities.com/~earlecj/cy/cy/index.htm
Edited by Christopher J. Earle
E-mail:earlecj@earthlink.com
Last modified on 20-Apr-1999

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