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Seed Plants Without Flowers (Division Coniferophyta: Conifers (simple…
Seed Plants Without Flowers
Division Pteridospermophyta: Seed Ferns
appeared first in upper devonian period
form a grade instead of a clade
pteridosperms
evolved from aneurophytales
the reason was due to three-ribbed protostele
ring of vascular bundles surrounding pith
occurs in stems of all gymnosperms and angiosperms
produce both xylem and phloem
Division Progymnospermophyat: Progymnosperms
aneurophytales
relictual progymnosperms
vary in shrubs to large trees
have vascular cambium and seccondary growth
archaeopteridales
trees
up to 8.4m tall
secondary phloem
stems
have siphonostele
reproduction was heterosporous
evolution of seeds
integument
layer of tissue
projects upward
micropyle
hole in integument
permits sperm cells to swim to eggs
pollen chamber
holding area
space at top of megasporangium
progymnosperms
evolved from trimerophytes
gave rise to conifers, cycads
Division Coniferophyta: Conifers
diverse plant
redwoods of california
grow to 90m in height and 10m in diameter
never vines, herbs, or annuals
no bulbs or rhizomes
leaves
simple needles or scales
simple cones
single short unbranched axis that bears microsporophylls
microspore mother cells
undergo meiosis
eventually develop into gametophyte
creates four cells
compound cones
consisting of a shoot with axillary buds
cone bracts
short axis bear leaves
each bract has axillary bud
bud bears megasporophylls
ovuliferous scale
microscopic axillary bud and megasporophylls are fused laterally
suspensor
first cells elongate that push other cells deep into the megagametophyte
proembryo
other cells develop into embryo
Division Cycadophyta: Cycads
confused with either ferns or young palm trees
most are short plants
macrozamia can reach 18m
cycad foliage don't bear ovules
produce seed cones and pollen cones
always dioecious
contains 9 or 10 genera
approximately 100 species
modern cycads are highly prized ornamentals
Division Cycadeoidophyta: Cycadeoids
vegatative features
almost identical to cycads
differ from cycads
by the differentiations of stomatal complexes andin leaf trace organization
contain both microsporophylls and megasporophylls
Division Ginkgophyta: Maidenhair Tree
single species of Ginko biloba
large dicot tree with a stout trunk
wood is like conifers
lacks vessels and axial parenchyma
have short and long shoots
reproduction is dioecious
popular ornamental
leaves turn brilliant yellow in autumn
Division Gnetophyta
gnetums
mostly vines or small shrubs
native
southeast Asia, tropical Africa, and Amazon Basin
ephedra
tough shrubs and bushes
very common in desert regions
leaves are reduced and scale like
welwitschia
deserts of South Africa or in cultivation
short, wide stem and only two leaves
