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Seed Plants I: Seed Plants Without Flowers (“Gymnosperms”) - Coggle…
Seed Plants I: Seed Plants Without Flowers
(“Gymnosperms”)
Division Progymnospermophyta: Progymnosperms
Archaeopteridales
trees up to 8.4 m tall with abundant wood
secondary phloem
heterosporous reproduction
Megaspores were released from the sporangia
siphonostele
Seeds were not produced
Evolution of Seeds
spores identified with sporophytes
spores were trapped in a sporangium
megasporangium surrounded by layer of tissue
Aneurophytales
secondary growth,
the primary xylem of their stems was a protostele
They all had a vascular cambium
further resembled trimerophytes
Micropyle
#
a hole in integument that permittef sperm cell to swim to the egg
Division Pteridospermophyta: Seed Ferns
classified as three
division
Cycadophyta (cycads,
extant)
Cycadophyta (cycads,
extant)
Pteridospermophyta (seed ferns, all extinct)
evolved from the Aneurophytales
three-ribbed protostele
Tracheids were much longer and wide enough
had a ring of vascular bundles surrounding a pith
Seed fern wood was manoxylic
Seed fern wood was manoxylic
the megasporangium
was large
Division Coniferophyta: Conifers
Leaf veins have an endodermis
transfusion parenchyma cells and transfusion tracheids
venation of conifer leaves is often simple
Transfusion parenchyma is intermixed with the tracheids
approximately 50 genera and 550 species
Division Cycadophyta
short plants less than 1 or 2 m tall
The trunk is covered with bark and persistent leaf bases
they have stout trunks with pinnately compound leaves
prominent pith contains secretory
canals
Modern cycads are highly prized ornamentals
Division Ginkgophyta: Maidenhair Tree
looks very much like a large dicot tree
Ginkgos have both long &short
shoots,
contains a single living species
ovules occur in
pairs at the ends of a short stalk
it lacks vessel and axial parenchyma
Division Cycadeoidophyta: Cycadeoids
#
both microsporophylls and
megasporophylls
microsporophyll was cup shaped
Each ovule had a stalk
had vegetative features
contained numerous microsporangia
Division Gnetophyta
contains 3 groups of enigmatic plants
mostly vines or small shrubs with broad leaves
compound cones
#
single short unbranched axis that bears microsporophyll
