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Ch 22 Seed Plants I: Seed Plants Without Flowers ("Gymnosperms")
Ch 22 Seed Plants I: Seed Plants Without Flowers ("Gymnosperms")
Division Progymnospermophyta: Progymnosperms
Aneurophytales
relictual progymnosperms
vary from shrubs to large trees
little webbing between branches
Archaeopteridales
more derived progymnosperm
reproduction was heterosporous
Evolution of Seeds
difficult but not impossible
integument
layer of tissue that projects upward
micropyle
hole in integument that permitted sperm cells to swim to the egg
pollen chamber
holding area
progymnosperms
later gave rise to conifers, cycads, and other gymnosperms
Division Pteridospermophyta: Seed Ferns
earliest seed fern appeared in Upper Devonian Period
Three Divisions
Pteridospermophyta
seed ferns all extinct
Cycadophyta
cycads, extant
Cycadeoidophyta
cycadeoids, all extinct
Division Coniferophyta: Conifers
50 genera
550 species
two different types of shoots
long shoot
tiny papery leaves occur here
short shoot
long needle leaves
simple cones
single short unbranched axis that bears microsporophylls
compound cones
shoot with auxiliary buds
cone bracts
short axis bears leaves
ovuliferous scale
auxiliary bud and megasporophylls fused laterally
suspensor
pushes other cells deep into megagametophyte
proembryo
other cells develop into embryo
Division Cycadophyta: Cycads
frequently confused with ferns
do not ovules
9-10 genera
100 species
Division Cycadeoidophyta: Cycadeoids
ALL EXTINCT
had vegetative features
almost identical to cycads
Division Ginkgophyta: Maidenhair Tree
single living species
leaves turn yellow in autumn
ancestors are not known
Division Gnetophyta
mostly vines or small shrubs
similar leaves to dicots
