Systematics of Cycadophyta

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Systematics of 

Cycadophyta

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Cycads: Description Large crown of pinnately compound leaves;

stout trunk; evergreen

Branched roots (coralloid roots) containsymbiotic cyanobacteria

Subtropical and tropical; produce poisonous

glycosides called cycasins

Jurassic period: age of cycads

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Classification, Cycadophyta

Cycadaceae- leaves pinnate, arranged

spirally, with thick and hard keratinose;

leaflets are articulated, have midrib but lacksecondary veins; caudex is cylindrical; have

cataphylls (reduced scalelike leaves). Ex.

Cycas

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cataphylls

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Cycas revoluta

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Cycas revoluta

Female cone

Male cone

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Cycas circinalis

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Cycas circinalis

Young seed, cs

megasporophylls

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Cycas circinalis

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Zamiaceae- superficially palm- or fernlike;

stem cylindrical, usually subterranean &

unbranched, tall and erect; leaves pinnate,spirally arranged; male & female sporophylls

are spirally aggregated into cones that grow

along the axis; geographical range:

Australia, South Africa Ex. Z amia,Macrozamia, Encephalartos, Ceratozamia

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Z amia integrifolia

Female

cone with

ripeseeds

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Z amia pumila

(female cones)

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Coralloid roots of Macrozamia douglasii Female cones, Macrozamia

miguelii 

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Ceratozamia

mexicana

microsporophylls

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Encephalartos woodii 

Male cone

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Encephalartos longifolius

Female cones

Male cones

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Encephalartos

ferox 

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Stangeriaceae- smallest cycad family; with only

2 extant genera, S tangeria & Bowenia; occursonly in South Africa & Queensland, Australia; with

vascularized stipules; lack cataphylls; stem large

and tuberous, completely subterranean, roots

contractile; Stangeria doesn¶t produce cataphylls;

cones greenish, with wooly covering of silvery to

brownish hairs; Bowenia entirely restricted to

Australia, has cataphylls, & is the only cycad with

bipinnate leaves.

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S tangeria eriopus

Female

cone

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Bowenia spectabilis

Male cones

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Bowenia serrulata

Male cones

Juvenile female cone

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Bowenia serrulata

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Systematics of 

Gnetophyta

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GnetaceaeDescription: evergreen trees,

shrubs or lianas; possess

vessel elements ; strobilus

fruit-like and seed nut-like;native to southeast Asia &

western Pacific Ocean

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G netum parvifolium

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G netum gnemon

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Gnetum seed

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Ephedra equisetinaEphedra sinica

Erect or partially procumbent

shrub; pollen cones solitary or 

in clusters; seed cones usuallyopposite at nodes, shortly

pedunculate, red & fleshy at

maturity; usually 1 seed

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Ephedra viridis

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W elwitschia

Description: monotypic genus; restricted to south-

west Africa (Namibia and Angola); trunk short & thick,

with only 2 leaves that continuously grow from their 

base and split into several strap-shaped sections;

growth is always sideways (obconical stem);

dioecious; CAM plant; one of the oldest plants in

existence (disc. by Friedrich Welwitsch in 1860)

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1.4 m tall,

over 4 m in

diameter 

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W elwitschia mirabilis, female

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W elwitschia mirabilis

Male plant

Female plant