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Cycas cairnsiana Photo Ken Hill
The Cycad Pages
Cycad Identification
The cycads are members of an ancient and very distinct natural group botanically known as the Cycadophyta or Cycadales. This group has been divided into three families and 11 genera. A key distinguishing families and genera is at the foot of this page, and each family and genus has its separate home page. Each genus page has links for all accepted species in that genus and keys to identify them. Evolution and distribution are discussed on other separate pages. You can also search the World List of Cycads for any cycad name.
Cycad classification
The following detailed classification (from Stevenson 1992) aims to accurately reflect
inferred evolutionary relationships among the living cycads.

OrderSuborderFamilySubfamilyTribeSubtribeGenus
CycadalesCycadineae Cycadaceae Cycas
Zamiineae Stangeriaceae Stangerioideae Stangeria
Bowenioideae Bowenia
Zamiaceae EncephalartoideaeDiooeae Dioon
EncephalarteaeEncephalartinae Encephalartos
Macrozamiinae Macrozamia
Lepidozamia
ZamioideaeCeratozamieae Ceratozamia
ZamieaeMicrocycadinae Microcycas
Zamiinae Zamia
Chigua

Cycad identification
Try this experimental multiple-entry key based on the DELTA format.
There is also a more traditional dichotomous key lower on the page.

Leaflet midrib

present
absent 		Secondary veins

present
absent 		Habit

subterranean
above-ground 		Leaflet insertion

on rachis sides
on rachis midline
Leaflet abscission

present
absent 		Leaflet basal callus

present
absent 		Leaves

simply pinnate
bipinnate 		Leaves

apically truncate
not truncate
Megasporophylls

not in cones
gathered in cones 		Sporophylls

in vertical rows
spirally arranged 		Sporophyll apex

a single prominent spine
two short spines
blocky, faceted
broadly flattened

Dichotomous key

1 Leaflets with a single midrib and no secondary veins -- Cycas
1* Leaflets with multiple veins
2 Leaves bipinnate -- Bowenia
2 Leaves once pinnate
3 Leaflet venation pinnate -- Stangeria
3* Leaflet venation parallel
4 Leaflet abscission present; sporophylls in spiral rows
5 Leaflet insertion on rachis midline -- Lepidozamia
5* Leaflet insertion on rachis sides
6 Leaflet basal callus present; sporophylls with a sharp upturned spine -- Macrozamia
6* Leaflet basal callus absent; sporophylls without a sharp upturned spine
7 Sporophylls with broad flattened upturned and overlapping apices -- Dioon
7* Sporophylls with blocky, faceted apices, not upturned & overlapping -- Encephalartos
4* Leaflet abscission absent; sporophylls in vertical rows
8 Leaflets with a discernable midrib -- Chigua
8* Leaflets lacking a discernable midrib
9 Leaves apically truncate -- Microcycas
9* Leaves not apically truncate
10 Sporophylls with 2 horns -- Ceratozamia
10* Sporophylls lacking horns -- Zamia
The Cycad Pages
© Royal Botanic Gardens Sydney
Written and maintained by Ken Hill
Please send comments and corrections