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Seed Plants without Flowers (Division Seed Ferns (appeared in the Upper…
Seed Plants without Flowers
Division Progymnosperms
now extinct
developed megaphyllous leaves
evolution of a vascular cambium (unlimited growth with secondary xylem/phloem)
no seeds/ovule precursors :forbidden:
Aneurophytales
more relictual progymnosperms
varied in stature
shrubs to large trees
had vascular cambium and secondary growth
stem primary xylem was protostele
resembled trimerophytes
Archaeopteridales
more derived progymnosperm
tress up to 8.4 m tall
abundant wood and secondary phloem
stems had a pith surrounded by a ring of primary xylem bundles
"fronds" resembled fern leaves
heterosporous reproduction
evolution of seeds
earliest known progymnosperm species with heterospory is Chauleria
megasporangium surrounded by integument
large micrpyle in the integument for the sperm to swim
megasporangium closely surrounded by sterile telomes
pollen chambers is where microspores settled
telomes became cupules
microspores evolved into pollen grains
Division Seed Ferns
appeared in the Upper Devonian period
form a grade not a clade
woody plant with fern like foliage that had seeds
resembled modern tree ferns
stem cells were parenchyma with a ring of vascular bundles surrounding the pith
tracheids longer and wider
rays were many cells wide
wood was manoxylic
Division Conifers :evergreen_tree:
most diverse
modern to gigantic size
they are perennial
leaves are simple needles or scales
veins have endodermis and transfusion tissues
wood lacks vessel and sieve tubes
has woody pollen and seed cones
pines are in this group
trees are monopodial
two types of shoots
long shoots
short shoots
has pollen/seed cones
pollen cones are simple cones :male_sign:
seed cones are compound cones :female_sign:
Division Cycads
stout trunks with pinnately compound leaves
trunk covered with bark and leave bases
similar to seed ferns
has seed/pollen cones
Division Cycadeoids
all extinct :warning:
similar to Cycads
different stomatal complexes and leaf trace organization
cones contain both micro/megasporophylls
Division Maidenhair tree
one species
wood like conifers
unknown ancestors
Division Gnetophyta
Ephedra shrubs and bushes
Gnetums are vines or small shrubs
Welwitschia have short wide stems with two leaves
