Dichotomous Key/Cycas

Key to the species of Cycas:

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

 * Cycas chanfjiangensis
 * Cycas miquelii

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


 * Cycas chevalieri:
 * Cycas fugax:
 * Cycas hoabinhensis:

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


 * Cycas balansae
 * Cycas brachycantha
 * Cycas simplicipinna

CYC62
unfinished


 * Cycas collina
 * Cycas dolichophylla
 * Cycas guizhouensis
 * Cycas segmentifida
 * Cycas yunnanensis

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


 * Cycas clivicola
 * Cycas elongata
 * Cycas tansachana

CYC66
unfinished


 * Cycas condaoensis
 * Cycas pachypoda

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


 * Cycas papuana
 * Cycas xipholepis

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


 * Cycas badensis
 * Cycas schumanniana
 * Cycas yorkiana