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Seed Plants I: Seed Plants Without Flowers (Gymnosperms) (Division…
Seed Plants I: Seed Plants Without Flowers (Gymnosperms)
Division Coniferophyta: Conifers
Wood of modern conifers lacks vessels and the phloem lacks sieve tubes
Pollen cones and seed cones
Trees moderate to gigantic size
Suspensor and proembryo allow fertilization to take place
Division Progymnospermophyta: Progymnosperms
Archaeopteridales
Trees up to 8.4 meters with abundant wood and secondary phloem
Reproduction in archaeopterids was heterosporous
Evolution of Seeds
Integument and micropyle allow heterosporous reproduction
Microspores settled in the pollen chamber
Aneurophytales
From shrubs to 12 meter trees
Vascular Cambium and Secondary Growth, but primary xylem looks like those of rhyniophytes and trimerophytes
Division Cycadeoidophyta: Cycadeoids
They differ with stomatal complexes and leaf trace organization
Contained both microsporophylls and megasporophylls
All extinct and have vegetative features identical to Cycads
Division Gnetophyta
Gymnosperms with vessels in their wood
Groups consist of small, tough, or desert shrubs
Three groups: Gnetum, Ephedra, Welwitschia mirabilis
Division Pteridospermophyta: Seed Ferns
Long-lived vascular cambium that produced xylem and phloem
Foliage leaves bore seeds
Appeared in Upper Devonian Period
Division Ginkgophyta: Maidenhair Tree
Looks like a large dicot tree, but the wood is that of a conifers
Ovules are completely unprotected
Contains a single living species, Ginkgo biloba
Division Cycadophyta: Cycads
Cycads are always dioecious
Almost all are tropical
Most Cycads are short plants 1-2 meters tall
