The sago or "King Sago" (Cycas revoluta Thunberg) is a member of the Cycadaceae or cycad family of the gymnosperms. Cycads are one of the oldest lineages of plants and, other than the extinct seed ferns, are considered the oldest line of seed bearing plants. A fossil specimen, Cycas fujiiana, is very similar to Cycas revoluta and dates to Eocene deposits, 34 to 55 million years ago.

Cycas revoluta is native to Satsuma, Mitsuhama Ito, and the Ryukyu Islands south of Japan. Once limited to those islands, the sago is now the most widely cultivated of the Cycas. Cycads are frequently confused with palms, but they are not flowering plants like palms.

Cycads are dioecious; the male has microsporophylls or "little-spore leaves" that produce pollen arranged in a strobilus (pl. strobili, the bright yellow cones in the photo) and the female has megasporophylls or "big-spore leaves" that produce ovules. These appear as fuzzy yellow-brown distorted leaves and bear the seeds along the leaf edges.

When the pollen is ripe, the strobilus opens and sheds its pollen to the wind. There is evidence that beetles or weevils may play a role in pollination. The pollen is unique in that it contains flagellated sperm cells that 'swim' the pollen tube to the ovule.

The seed of Cycas revoluta is covered with a fuzzy, bright orange, fleshy sarcotesta. The seeds are shed before the embryo is mature. The sarcotesta contains germination inhibitors which apparently gives the embryo time to mature. This after ripening (embryo maturity) takes six to twelve months and until the sarcotesta rots or is removed the seed will not spout.

The Palm and Cycad Societies of Australia (PACSOA) has a photograph of a female Cycas revoluta with seeds. To view the photograph, click on the link: http://www.pacsoa.org.au/cycads/Cycas/revoluta.html