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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