Cycadaceae
(Cycads)
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Habit
- pachycaul, unbranched,
palm-like (old leaf-bases
remain),
dioecious trees 
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Leaves
- pinnately compound; developing like ferns.... (circinate
vernation); cataphylls also present
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Ovules
- in cones on peltate
scales or on edges of modified leaves
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Sperm
- largest known (300 um); motile
with spiral band of flagella;
sex determined by X and Y chromosomes
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Seeds
- covered with fleshy seed
coat
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Diversity
- 10 genera / ca. 100 species of the tropics
in 1 family (older texts) or 2 families (the more recent treatments) :
- Cycadaceae (pinnae
with no lateral veins;
ovules on leaf-like sporophylls; Cycas, ca. 20 spp., sago-palm)
- Zamiaceae (pinnae with numerous parallel or wavy, simple or forked veins;
ovules in cones; 8 genera, 85 species)
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Distribution
- tropics world-wide
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Economics
- all cultivated ornamentals and endangered through over-collecting; some
yield sago (starch for bread
in India)
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Notes
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Images
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