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Seed Plants I: Seed Plants without Flowers "Gymnosperm",…
Seed Plants I: Seed Plants without Flowers "Gymnosperm"
Division Coniferophyte: Conifers
Venation conifer leaves is simple
never vines, herbs or annuals
diverse and moderated to large size
50 genera and 550 species
lack of bulb or rhizomes
Compound Cones
Single short unbranched axis
bears microsporophylls
Division cycadophyte: Cycads
Thick cortex contains secretory ducts
small amount of manoxylic
short plants less than 1m or 2m tall
confused among fern or young palm trees
trunk covered with bark
persistent leaf bases
Division Ginkgophyte: Maidenhair tree
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unusal to erect
single living species ginkgo biloba
large dicot tree
lack vessels and axial parenchyma
Division Progymnospermophyta: Progymnosperm
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Micropyle
Hole in the integument
Permitted sperm cells to swim
And goes to egg
Evolution of seeds
megasporangium was surrounded
Fossil material is difficult
but not impossible
Spores can be identified with sporophytes
Aneurophytales
Have vascular cambium and secondary growth
contains more relictual progymnosperm
Looks like shrubs trees
primary xylem was protostele like rhyniophytes
Archaeopteridales
Reproduction was hetererosporous
Progymnosperm was Archaeopteris
up to 8.4m tall
megaspores were released from the sporangia
Division Genetophyta
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Native to south east Asia, tropical Africa and amazon basin
contains three groups of enigmatic plants
Gnetums are mostly vines with broad leaves
Division Pteridospermophyta: seed ferns
attached to megasporangium
manoxylic, softer and less dense
progymnosperms gave rise
three division
seeds are large, compound and planar
Division Cynaceoidophyta: Cycadeoids
Cup shaped
cycadeoids would never be considered distinct from cycads
have vegetative features
two groups differ only in subtle details
contain both microsporophylls and megasporophylls
Functional Connection
Differential connection
types connection
