1. Nonflowering Seed Plants
Chapters 21 & 22
Seedless Vascular and
Nonflowering Seed Plants

2. Topics Rhyniophytes Evolution of stele – protostele and syphonostele
Vascular plant cladogram
Phylum – Lycophyta
Phylum – Pteridophyta – life cycles
Adaptive superiority of the seed
Gymnosperm phyla

3. Early Vascular Plants: Extinct Rhyniophytes
Cooksonia spp. - Rhynia spp. branching sporophyte – homosporous
Today sporangia on vascular plants are lateral – not terminal

4. Early Vascular Plants
Similarities between the hornworts and vascular plants make Anthoceros the possible ancestors of vascular plants – inner vascular cylinder = stele
Protostele – solid – no pith – more ancestral
Lycophyte stem & root, seed plant roots too
Siphonostele – central pith - stems of ferns and seed plants – more derived - will discuss in plant tissues later
Protostele Siphonostele

5. Microphylls from enations/scales
Megaphylls from branch systems

6. (ground pine, club moss)
Phylum - Lycophyta
Lycopodium sp.
(ground pine, club moss)
Selaginella sp.
Label – Strobilus axis,
microsporangium,
megasporangium, seta,
microsporophyll,
megasporophyll,
microspores, megaspores
HETEROSPORY
Label – Strobilus axis,
sporangium, seta,
sporophyll, spores
HOMOSPORY

7. Phylum - Pteridophyta – Ferns and allies
Psilotum spp.
Whisk ferns

8. Equisetum spp.
Horsetails
Strobilus

9. Ferns - >12,000 spp.
Fern stem
Fern root

11. Ferns: Life Cycle

12. Seed – superior propagation
Gymnosperms
Seed – superior propagation
Heterospory - Megasporangium to megaspore to megametophyte to archigonium – all in ovule = egg and other cells = megagametophyte - retained inside the maternal sporophyte
Fertilized ovule = sporophytic embryo - could use the photosynthetic and absorptive capacity of leaves and roots of mother sporophyte – rather than depending on a tiny haploid gametophyte
Seed ferns are all extinct

13. Seed Fertilized ovule covered by its integument - seed coat
Embryonic sporophyte
Nutritive tissue to nourish sporophyte
Dormant period
Not covered by an ovary = Gymnosperms
Gymnosperms <1000 spp.
Four phyla

14. Phylum - Cycadophyta: Cycads
Only ~100 species today
Almost all tropical
Dioecious – seed cones
and pollen cones on
separate plants

15. Phylum - Ginkgophyta: Maidenhair Tree
single living species, Ginkgo biloba
Broad leaves – veins dichotomously branched – not reticulate
Dioecious – seeds not on cones – emits butric acid – foul odor
Native to China – medicinal uses

16. Phylum Coniferophyta = Pinophyta
Most diverse Gymnosperms - >550 spp.
All moderate to extremely large trees
(Sequoia spp. - largest organisms on
planet)
Mainly monoecious

19. Phylum - Gnetophyta ~ 70 spp.
Gnetum spp.
Ephedra spp.
Vessels and
sieve tubes
Similarity to
Anthophytes
Many – dioecious
some - monoecious
Welwitschia mirabilis
Only sp. in genus