Seed Plants I: Seed Plants Without Flowers ("Gymnosperms")…
Seed Plants I: Seed Plants Without Flowers ("Gymnosperms")
Division Progymnospermophyta: Progymnosperms
Order Aneurophytales contains the more relictual progymnosperms.
They varied in size from shrub to large trees
They all had a vascular cambium and secondary growth, but the primary xylem of their stems was a protostele like that of rhyniophytes and trimerophytes.
A more derived progymnosperm was Archaeopteris in the order Archaeopteridales.
Trees up to 8.4 m tall with abundant wood and secondary phloem.
Evolution of Seeds
The current earliest known progymnosperm species with heterospory is Chauleria from the Middle Devonian Period.
Division Pteridospermophyta: Seed Ferns
Division Coniferophyta: Conifers
Division Cycadophyta: Cycads
Division Cycadeoidophyta: Cycadeoids
Division Ginkgophyta: Maidenhair Tree
are those plants with "naked ovules". Ovules located on flat sporophylls.
Flowering plants, those with carpels, which are believed to be sporophylls that form a tube-like closed structure.