10/20/12

1

Ch 21: Early Vascular Plants = non-seed plants

Trends:

sporophyte becomes dominant, gametophyte reduced

spores: homospory - > heterospory

sperm still swim

true plant organs appear

stems first

roots

leaves

microphylls - > megaphylls

vascular tissue: xylem & phloem

Earliest identifiable fossil vascular plants

P: Rhyniophyta

Dichotomous branching

stems

10/20/12

2

P: Lycophyta

Lycopodium = club moss, ground pine/cedar

strobilus

microphylls

Lycopodium life cycle (homosporous)

2N adult

1N adult mitosis

mitosis

(underground)

Lycopods were once trees (and microphylls were not small) Carboniferous Period

10/20/12

3

http://www.youtube.com/watch?v=F3ChXba3dus

Selaginella = spike moss

Selaginella life cycle (heterosporous)

heterosporous

with sperm

mitosis

mitosis

mitosis

2N adult

1N adult

1N adult

mitosis

(underground)

(underground)

10/20/12

4

Selaginella lepidophylla = resurrection plant

dry

wet

Isoetes = quillwort

P? Psilotophyta = whisk ferns

Only 2 genera left eg: Psilotum

10/20/12

5

P? Equisetophyta = horsetails, scouring rushes

Only 1 genus left: Equisetum

Have green, hollow stems

Horsetails were once trees (reconstruction of a Devonian swamp)

10/20/12

6

P: Polypodiophyta = ferns

Fern life cycle (usually homosporous, but a few species are heterosporous)

1N adult

2N adult

sperm

mitosis

mitosis (above ground)

Fern 1N gametophyte = prothallium

(above ground, photosynthetic)

10/20/12

7

Fern life cycle focus on sporophyte (2N)

Sorus holds

sporangium/ia

indusium

Megaphyll leaves

10/20/12

8

fiddle-neck = crozier: spiral unfolding of young leaves