Dichotomous Key/Cycadophyta

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Dichotomous Key

Kingdom	Plantae
Division	Cycadophyta
Class	Cycadopsida
Order	Cycadales

This is the key to species of Cycadophyta.

Key to the species of Cycadophyta

Cycas: Pinnae have a single midrib and lack secondary veins
1: Pinnae have more than one vein

1

Bowenia: Leaves are bipinnate
2: Leaves are once-pinnate

2

Stangeria eriopus: Leaves with pinnate venetion.
3: Pinnae have parallel venetion

3

4: Sporophylls in vertical rows
5: Sporophylls in spirals

4

Chigua: Pinnae have an obvious midrib
6: Pinnae lack an obvious midrib

5

Lepidozamia: Pinnae attach to midline of rachis
8: Pinnae attach to sides of rachis

6

Microcycas calocoma: Leaves are square or broad at the end.
7: Leaves are not broad or square at the end.

7

Ceratozamia: Sporophylls have two horns.
Zamia: Sporophylls lack horns

8

Macrozamia: Sporophylls have a sharp upturned spine
9: Sporophylls lack a sharp upturned spine.

9

Dioon: Sporophylls have flat overlapping tips.
Encephalartos: Sporophyll tips do not overlap

Bowenia

Bowenia spectabilis: One to ten leaf bearing branches; Largest leaves have ten or less pinnae; Pinnules usually entire, or nearly so.
Bowenia serrulata: Five to twenty leaf bearing branches; Largest leaves have more than ten pinnae; Pinnules toothed or lobed.

Ceratozamia

unfinished

Chigua

Chigua bernalii: Pinnae are over 30 centimeters long and less than 20 millimeters wide.
Chigua restrepoi: Pinnae are less than 30 centimeters long and over 20 millimeters wide.

Cycas

CYC1: Ovules coated with hair.
CYC2: Ovules lacking hair.

CYC1

Cycas taitungensis: Pinnae flat
Cycas revoluta: Pinnae rolled near the tip

CYC2

CYC3: Expanded portion of Megasporophyll leaf with closely parallel toothlike projections.
CYC4: Expanded portion of megasporophyll leaf without closely parallel toothlike projections.

CYC3

CYC5: Male cones are stiff and rigid
CYC6: Male cones are soft

CYC4

CYC10: Spongy tissue present in seeds.
CYC11: Spongy tissue not present in seeds.

CYC5

CYC7: Hard seed coat is ribbed.
Cycas panzhihuaensis: Hard seed coat is not ribbed.

CYC6

CYC8: Soft seed coat is not fibrous; hard seed coat is studded with wart-like projections
CYC9: Soft seed coat is fibrous; hard seed coat is smooth.

CYC7

Cycas curranii: Pinnae over 6 millimeters wide; seeds over 40 millimeters long.
Cycas wadei: Pinnae less than 6 millimeters wide; seeds less than 40 millimeters long.

CYC8

CYC14: Top of megasporophyll spine much longer and wider than lateral spines
CYC15: Top of megasporophyll spine similar to lateral spines

CYC9

Cycas lindstromii: Male cones less than 5 centimeters in diameter; Stems underground
CYC17: Male cones over 5 centimeters in diameter; stem rises at least partially above ground.

CYC10

CYC20: Seeds have a wing on the tip
CYC21: Seeds do not have an obvious wing on the tip

CYC11

CYC12: Hard seed coat has a fibrous layer
CYC13: Hard seed coat does not have a fibrous layer.

CYC12

Cycas beddomei: Pinnae less than 5 millimeters wide
CYC27: Pinnae over 5 millimeters wide.

CYC13

CYC37: Basal pinnae gradually reducing in size
CYC38: Basal pinnae not gradually reducing in size

CYC14

CYC49: Pinnae less than 11 millimeters wide.
CYC50: Pinnae over 11 millimeters wide

CYC15

CYC54: Pinnae simple
CYC55: Pinnae dichotomously divided

CYC16

Cycas chamaoensis: Male cones rounded and tapering from the middle toward each end; Spindle-shaped
CYC63: Male cones elliptical or oval-shaped

CYC17

Cycas hongheensis: Leaves have a distinct longitudinal ridge and covered with hair.
CYC19: Leaves mostly flat and at least the top is without hair.

CYC18

Cycas siamensis: Basal pinnae reducing to spines
CYC64: Basal pinnae not reducing to spines.

CYC19

CYC16: Phelloderm smooth
CYC18: Phelloderm corky

CYC20

Cycas rumphii: Megasporophyll lateral spines are small bumps
CYC22: Megasporophyll lateral spines distinct

CYC21

CYC23: Pinnae are broad, very glossy, and bright green
CYC24: Pinnae are slightly glossy; Pinnae are bluish when new

CYC22

Cycas micronesica: Apical spine is less than 15 millimeters long
CYC25: Apical spine is over 15 millimeters long

CYC23

Cycas edentata: Plants found in the Philippines.
Cycas litoralis: Plants found in Thailand

CYC24

Cycas thouarsii: Fewer broad, short cataphylls present. Plants of Madagascar
Cycas zeylanica: Numerous thin, long cataphylls present. Plants of Sri Lanka.

CYC25

Cycas boubainvilleana: Pinnae over 12 millimeters wide
CYC26: Pinnae less than 12 millimeters wide.

CYC26

Cycas falcata: Petioles usually spiny.
Cycas seemannii: Petioles without spines, or with few spines.

CYC27

CYC28: Pinnae less than ten millimeters wide
CYC29: Pinnae over ten millimeters wide.

CYC28

CYC30: Lateral megasporophyll teeth less than four millimeters long.
CYC31: Lateral megasporophyll teeth over four millimeters long.

CYC29

Cycas pranburiensis: Petioles lacking spikes or bristles
CYC32: Petioles have spines or bristles

CYC30

Cycas circinalis: Megasporophyll lamina 75 to 100 millimeters long. Plants of India
Cycas nathorstii: Megasporophyll lamina 40 to 70 millimeters long. Plants of Sri Lanka

CYC31

Cycas chamberlainii: Lateral spines on megasporophyll lamina over ten millimeters long.
CYC33: Lateral spins on megasporophyll lamina less than 10 millimeters long.

CYC32

Cycas macrocarpa: Lateral teeth of megasporophyll over seven millimeters long.
CYC34: Lateral teeth of megasporophyll less than seven millimeters long.

CYC33

Cycas riuminiana: Plants of the Philippines
Cycas spherica: Plants of India

CYC34

Cycas apoa: Lamina lacking lateral spines
CYC35: Lamina has distinct lateral spines or teeth.

CYC35

Cycas javana: Lamina thin and tapering toward the tip.
CYC36: Lamina egg-shaped.

CYC36

Cycas inermis: Stems 1 to 4 meters tall; 8 to 14 centimeters in diameter; Petiole is 60 to 80 centimeters long.
Cycas scratchleyana: Stems over 4 meters tall; 12 to 20 centimeters in diameter; Petiole is 20 to 70 centimeters long.

CYC37

CYC39: Lateral megasporophyll teeth large; Basal pinnae reducing to spines.
CYC40: Lateral megasporophyll teeth small; Basal pinnae not reducing to spines.

CYC38

CYC41: Hypodermis present; Leaf edges recurved.
CYC42: Hypodermis absent; Leaf edges flat.

CYC39

Cycas basaltica: Leaves are flat
CYC67: Leaves are keeled

CYC40

CYC68: Pinnae edges flat or recurved; Pinnae more than five millimeters wide.
CYC69: Pinnae rolled backward or downward; Pinnae less than five millimeters wide.

CYC41

CYC43: Hypodermis continuous; Leaves grey or blue.
CYC44: Hypodermis interrupted; Leaves green.

CYC42

Cycas canalis: New leaves glaucous blue
CYC70: New leaves green or bluish green

CYC43

CYC45: Leaves strongly glaucous; Male cones oval-shaped.
CYC46: Leaves not glaucous, or only slightly; Male cones large and spherical.

CYC44

CYC47: Spines and/or bristles present on cataphylls
CYC48: Spines and/or bristles not present on cataphylls

CYC45

CYC76: Pinnae edges rolled backward or downward; Pinnae less than four millimeters wide.
CYC77: Pinnae edges flat or recurved, but not rolled backward or downward; Pinnae over four millimeters wide.

CYC46

Cycas angulata: Pinnae are less than six millimeters wide.
Cycas brunnea: Pinnae are over six millimeters wide.

CYC47

Cycas megacarpa: Leaves are keeled over 135 degrees.
CYC75: Leaves are flat, or at least keeled less than 135 degrees.

CYC48

CYC79: Cataphylls and crown densely orange and wooly.
CYC80: Cataphylls and crown gray or white.

CYC49

Cycas hainanensis: Seeds relatively large
CYC51: Seeds relatively small

CYC50

Cycas taiwaniana: Twelve to thirty leaves in crown
Cycas tanqingii: Four to seven leaves in crown

CYC51

CYC52: Plants relatively large
CYC53: Plants relatively small

CYC52

Cycas tropophylla: Leaves keeled
Cycas ferrunginea: Leaves flat

CYC53

CYC54

CYC56: Microsporophylls coming to a short, abrupt point.
CYC57: Microsporophylls rounded

CYC55

CYC58: Pinnae dichotomously divided two to three times.
CYC59: Pinnae pinnately divided and dichotomously divided more than three times.

CYC56

unfinished

CYC57

Cycas diannanensis: Cataphylls long and rigid.
CYC60: Cataphylls short and soft.

CYC58

Cycas micholitzii: Leaves 110 to 240 centimeters long and moderately keeled (inserted at 90-120 degrees on rachis)
Cycas multifrondis: Leaves 200 to 500 centimeters long and flat to slightly keeled (inserted at 120-180 degrees on rachis)

CYC59

Cycas debaoensis: Megasporophylls are 12-14 centimeters long
Cycas multipinnata: Megasporophylls are 7-11 centimeters long

CYC60

CYC61: Male cones are small and narrow
CYC62: Male cones are large

CYC61

unfinished

CYC62

unfinished

CYC63

Cycas pectinata: Has long apical microsporophyll spine.
CYC65: Has a short apical microsporophyll spine.

CYC64

Cycas nongnoochiae: Male cones small
CYC66: Male cones medium to small.

CYC65

unfinished

CYC66

unfinished

CYC67

Cycas furfuracea: Pinnae margins flat or recurved; pinnae are over five millimeters wide
Cycas pruinosa: Pinnae margins are rolled backward or downward; pinnae are less than five millimeters wide.

CYC68

Cycas arnhemica: New growth with mostly brown or orange trichomes.
Cycas maconochiei: New growth with mostly white or grey trichomes.

CYC69

Cycas arenicola: Pinnae four to seven millimeters wide; 180-270 pinnae present.
Cycas calcicola: Pinnae two to four millimeters wide; 200-400 pinnae present.

CYC70

Cycas conferta: Pinnae the same color throughout and have stomata on upper and lower surfaces.
CYC71: Pinnae more or less different colors throughout and only have stomata on one side.

CYC71

CYC72: Cataphylls pale brown and hairy
CYC73: Cataphylls orange and wooly

CYC72

Cycas orientis: Midrib more prominent below than above.
CYC74: Midrib equally prominent above and below.

CYC73

Cycas armstrongii: Stems less than twelve centimeters in diameter.
Cycas lane-poolei: Stems over twelve centimeters in diameter.

CYC74

unfinished

CYC75

Cycas media: Pinnae are less than nine millimeters wide; Cataphylls are persistent.
Cycas silvestris: Pinnae are over nine millimeters wide; Cataphylls are deciduous.

CYC76

Cycas cairnsiana: Cataphylls soft and short.
Cycas desolata: Cataphylls sharply pointed and long.

CYC77

Cycas couttsiana: Main growth mostly gray or white trichomes.
CYC78: Main growth mostly orange or brown trichomes.

CYC78

Cycas ophiolitica: Pinnae six to eight millimeters wide; Leaves keeled at 80-120 degrees.
Cycas platyphylla: Pinnae four to six millimeters wide; Leaves keeled at 45-60 degrees.

CYC79

Cycas campestris: Lateral spines of megasporophyll lamina over 8 millimeters long.
CYC81: Lateral spines of megasporophyll lamina less than 8 millimeters long

CYC80

Cycas semota: Megasporophylls 18 to 25 centimeters long; Apex 15 to 35 millimeters wide and not dilated.
Cycas tuckeri: Megasporophylls 10 to 15 centimeters long; Apex 35 to 50 millimeters wide and dilated.

CYC81

unfinished

Dioon

DIO1: Leaflets straight
DIO2: Leaflets curved or hooked

DIO1

DIO3: Leaflets less than fifteen millimeters wide.
DIO4: Leaflets over fifteen millimeters wide.

DIO2

Dioon sonorense: Leaflets less than five millimeters wide.
Dioon tomasellii: Leaflets over five millimeters wide.

DIO3

Dioon edule: Leaflet edges entire.
DIO5: Leaflet edges with spines

DIO4

Dioon rzedowskii: Petiole without spines.
DIO6: Spines present on petiole.

DIO5

DIO7: Leaflets inserted at 90 degrees to rachis.
DIO8: Leaflets inserted at 45 degrees or less to rachis.

DIO6

Dioon mejiae: Leaflet edges entire.
Dioon spinulosum: Leaflet edges with spines.

DIO7

Dioon holmgrenii: Leaflets seven to nine millimeters wide; Leaflets do not overlap.
Dioon merolae: Leaflets en to twelve millimeters wide; Leaflets overlap.

DIO8

Dioon caputoi: Leaflets less than five millimeters wide; Leaflets flat and do not overlap.
DIO9: Leaflets over five millimeters wide; Leaflets keeled and overlap.

DIO9

Dioon califanoi: Leaflets seven to eight millimeters wide.
Dioon purpusii: Leaflets eight to ten millimeters wide.

Encephalartos

unfinished

Lepidozamia

Lepidozamia hopei: Pinnae have fifteen to thirty parallel veins; Broadest pinnae fifteen to thirty millimeters wide.
Lepidozamia peroffskyana: Pinnae have five to fifteen parallel veins; Broadest pinnae five to fifteen millimeters wide.

Macrozamia

unfinished

Zamia

unfinished

References

Jones, David L. Cycads of the World: Ancient Plants in Today's Landscape. Smithsonian Books: Reed, Sydney, 2002.
Walters, T. and Osborne, R. 2004. Cycad Classification Concepts and Recommendations. Wallingford UK: CABI Publishing.
Whitelock, Loran. The Cycads. Portland: Timber Press, 2002.

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