seed plants without flowers "gymnosperm" (division…
seed plants without flowers "gymnosperm"
division Progymnospermophyta: Progymnosperm
reproduction is heterosporous.
stem had a Siphonostele, pith surround by a primary xylem, like modern conifers
trees up to 8.4 m tall with abundant wood and secondary pholem.
evolution of seeds
Microspores evolving into pollen grains.
true seed plants is that they developed structures called cupules to enclose and protect the ovule
earliest known progymnosperm species with heterospory is Chauleria.
resembled trimerophytes having webbing between their branches, but not leaves.
varied in structure from shrubs, to large tress up to 12m tall.
contains more relictual progymnosperm.
pregymnosperm don't have seed or even ovule precursors.
division of Pteridospermatophyta: seed ferns
are very woody plant with fern-like foliage that bore seeds.
rays in pteridosperm wood were many cells wide.
earliest seed ferns appeared in the devonian period.
Division of Coniferophyta: conifers
venation is often simple, with just one or two long veins.
conifers are never vines, herbs, or annuals and never have rhizome or bulbs.
they are diverse, and all are gigantic size.
most are monoceious.
Division Cycadophyta: Cycad
most cycads are short plants less than 1 or 2 m tall
Cycad produce seed cones and pollen cones each on separate plants
confused with either fern or young palm trees.
discovered and described in mesozoic era.
Division cycadeoidophyta: cycadeoids
individual cone of Cycadeoids contains micro and mega spororphyll.
microsporophyll was located below the cluster of megasporophyll.
has vegetative features almost identical to those of cycads.
discovered and described from mesozoic era.
Division of Ginkgophyta: Maidenhair tree
looks like large dicot tree with stout trunk and many branches.
woods look life of conifers: lacks vessel and axial parenchyma.
contains single living species.
have both short shoots that bear leaves and long shoots.
is a vine found in tropical rainforests.
gnetophytes are compound and contain small bracts.
gnetophytes are heterosporous.
gnetophytes bear their reproductive structures in strobili, or cones.