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Cycadaceae Persoon

苏铁科 su tie ke

Authors: Jiarui Chen & Dennis W. Stevenson

Trees or shrubs evergreen, dioecious, mostly palmlike; trunk columnar, sometimes dichotomously branched at apex, rarely ovoid-bulbous and subterranean, clothed with bases of fallen leaves; bark often thickened and roughened. Leaves borne at apex of trunk, 1(-3)-pinnately compound, spirally arranged; new leaves erect (or somewhat inflexed and appearing coiled in C. multipinnata group), with circinnate leaflets; petiole with spines representing (reduced basal leaflets), rarely unarmed, base swollen and hairy; leaflets numerous, alternate to subopposite, dichotomously branched in a few species, midvein present, margin usually entire. Cataphylls prominent, alternate with leaves, hairy, apex often rigid and pungent. Pollen cones borne at apex of trunk, cylindric or fusiform; microsporophylls numerous, scalelike, spirally and tightly arranged along axis of cone, with numerous microsporangia in groups abaxially; pollen tubes producing 2 motile sperm cells. Megasporophylls several to numerous, somewhat leaflike, alternating with flushes of leaves, arranged in a loose, "conelike" crown surrounding apex of trunk, each with a linear fertile stalk and an apical, pinnatifid or subentire sterile blade; ovules (1 or)2-5 on each side of stalk. Seeds drupelike, somewhat compressed; seed coat 3-layered, consisting of colored sarcotesta, woody sclerotesta, and membranous endotesta. Cotyledons 2, united at base. Germination hypogeal, cryptocotylar. 2n = 22*.

One genus and ca. 60 species: E Africa (including Madagascar), E and S Asia, N Australia, Pacific Islands; 16 species (eight endemic) in China.

Ornamental species include Cycas revoluta, which is widely cultivated worldwide. Other species (e.g., C. circinalis Linnaeus, C. media R. Brown, C. pectinata, C. rumphii Miquel, C. taitungensis, and C. thouarsii R. Brown) have excellent ornamental qualities. The stem starch, "sago" (not to be confused with the true sago as obtained from palms of the genus Metroxylon Rottboøll), is edible and is used in packing brewers’ yeast after the removal of cycasins which are highly toxic and carcinogenic. A paste of Cycas seeds and coconut oil is used for the treatment of skin complaints, wounds, ulcers, sores, and boils.

Fu Shu-hsia, Cheng Wan-chün, Fu Li-kuo & Chen Chia-jui. 1978. Cycadaceae. In: Cheng Wan-chün & Fu Li-kuo, eds., Fl. Reipubl. Popularis Sin. 7: 4-17.

Lower Taxon


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