The cycads are seed plants, one of the groups on non-flowering seed plants that evolved in the Mesozoic, long before the first flowering plants. There are 9 or 10 genera of cycads and several hundred species mostly from the Southern Hemisphere. The cycad collection in Belfast Botanic Gardens is extensive and growing.
The cycads are a group of plants of mainly tropical and sub-tropical distribution. Below is a summary classification showing relationships between the genera. The table contains links to genera of which we have examples in the Tropical Ravine.

Cycadales (306 species)
Cycas (115 species)
Stangeria (1 species)
Bowenia (2 species)
Zamiaceae (divided into tribes and sub-families but containing the following genera)
Dioon (13 species)
Encephalartos (66 species)
Macrozamia (41 species)
Lepidozamia (25 species)
Ceratozamia (25 species)
Microcycas (1 species)
Chigua (probably included in Zamia)