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Seed Plants I: Seed Plants Without Flowers (Gymnosperms) (Division…
Seed Plants I: Seed Plants Without Flowers (Gymnosperms)
Concepts
Lignophytes
Monophyletic group of woody plants
Spermatophytes
Seed plants
Gymnosperm
Plants with ovules located on flat sporophylls
Angiosperm
Flowering plants with carpels
Carpels are sporophylls that form tube-like, closed structure
Division progymnospermophyta: progymnosperms
Aneurophytales
Contains the more relictual gymnosperms
Archaeopteridales
These were tall trees with abundant wood and secondary phloem
Evolution of seeds
Spores can be identified if trapped in a sporangium attached to leaves or wood during fossilization
Integument
Layer of tissue surrounding the megasporangium
Micropyle
A hole in the integument that permitted sperm to swim through to the egg
Named because they gave rise to cycads, conifers, and other gymnosperms
Division Pteridospermophyta: seed ferns
Form a grade, not a clade
Any woody plant with fern-like foliage
Bore seeds instead of sori
Division coniferophyta: conifers
All are trees of moderate to gigantic size
Never vines, herbs, or annuals
Never have bulbs or rhizomes
Leaves are perennial
Pines
Long shoots
Have tiny papery leaves
Short shoots
Produce long needle leaves
Simple cones
Pollen cones with a single short unbranched axis
Compound cones
Seed cones
Each consists of a shoot with axillary buds
Division cycadophyta: cycads
Most are short plants
Trunk is covered with bark
Stems are similar to those of seed ferns
Division cycadeoiphyta: cycadeoids
Have vegetative features similar to those of cycads
All extinct
Division ginkgophyta: maidenhair tree
One single living species
Has short shoots and long shoots
Looks like a large dicot tree with a stout trunk and many branches
Division gnetophyta
Mostly vines or small shrubs
Broad leaves similar to dicots
