Pteridophytes�Spore-bearing, Vascular Plants

Lycophytes

Ferns

Horsetails

Pteridophytes

• Ferns and “fern allies” were called pteridophytes
• Defining characteristics:
• Spore-bearing plants (no seeds)
• Vascular plants: true xylem and phloem
• …but not woody!
• Sporophyte dominant (larger)
• Gametophyte independent, but smaller
• Source of fossil fuels: coal
• Have many commercial uses: aesthetics, erosion control
• True ferns are the 3^rd largest plant group
• Ferns are diversifying and dominate in many areas

Plant Phylogeny

Pteridophytes are vascular plants

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Three lineages of vascular plants

1. Lycophytes (Clubmosses)
2. Ferns, Horsetails, etc.
3. Seed plants (Session 4-5)

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Leaves evolved independently in these groups

• …and separate from bryophytes

Pteridophytes

megaphylls

Bryophytes

Green algae

xylem &

phloem

Ferns

Horsetails

Seed plants

Lycophytes

microphylls

Terminology

• Megaphyll: “large” (true) leaves with branched veins found in ferns
• Microphyll: “small” leaves with a single vein

found in lycophytes

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• Homosporous: all spores the same size
• Heterosporous: spores are different sizes
• Megaspore: large spore (in megasporangium)

that germinates into a female gametophyte

• Microspore: small spore (in microsporangium) that germinates into a male gametophyte

“-phyll” means leaf

sporangium

“mega-” means large, but also female

“micro-” means small, but also male

gametophytes

megaphyll

microphylls

Fern & fern allies� phylogeny

• Feature: Megaphylls
• Ferns and horsetails both have complex anatomy

Whisk ferns

Horsetails

True Ferns

Seed plants

Bryophytes

Green algae

Lycophytes

True leaves

(Megaphylls)

True Ferns

• Successful spore-bearing plants, 12K spp.
• Large, true leaves (Megaphylls)
• Usually compound, called “fronds”
• Young leaves called fiddle heads
• Stems are rhizomes with adventitious roots
• Sporangia on the underside of leaves
• Sporangia cluster into a sorus
• Homosporous & heterosporous taxa
• Each sporangium has annulus

Fern orders

• Polypodiales (80% of ferns)
• Osmundales (Royal ferns)
• Cyatheales (Tree ferns)
• Schizaeales
• Salviniales (Water ferns)
• Only heterosporous ferns
• Azolla has cyanobacteria
• Hymenophyllales (filmy ferns)

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Schizaea pusilla - curlygrass fern

Osmunda regalis

royal fern

Claytosmunda

interrupted fern

Crepidomanes intricatum - weft fern

Azolla – mosquito fern

Marsilea – cloverleaf fern

Salvinia – velvet fern

Osmundastrum cinnamomeum

cinnamon fern

Fern Lifecycle

Mature

Sporophyte (2n)

Roots

Rhizome

Leaflet or

Pinna

Leaves or

Fronds

Leaf = frond

Leaflet = pinna

Fiddlehead

Meiosis

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Spores (1n)

Sporangium

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Spore

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Gametophyte

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spore

Fern gametophyte, x100

rhizoids

Antheridia (n)

Fertilization

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Grows up into mature fern

Horsetails & �Scouring Rushes

• 1 genus (Equisetum); 15 species
• Bamboo-like stems
• Whorled leaves and stems
• Leaves reduced
• Sporangia in a cone
• Spores with elaters
• Live in wetland environments
• Absorb silica and other macromolecules from soil

Gametophyte

Equisetum myriochaetum

Equisetum arvense

elaters

Equisetum palustre

Equisetum fluviatile

Equisetum hyemale

elaters

Equisetum hyemale

Common scouring rush

Whisk ferns

• 2 genera; 4 species
• Psilotum, Tmesipteris
• Tropical, herbaceous plants
• Equal-branching stems
• Rhizome but no roots
• Scales but no leaves
• Simple large sporangia
• Gametophyte subterranean & dependent on mycorrhizae

Tmesipteris

Psilotum

Plant phylogeny

Vascular plants split into two main lineages

• Lycophytes
• Microphylls

Ferns/Horsetails

Seed plants

Bryophytes

Green algae

Lycophytes

Lycophytes�or Clubmosses

• Equal-branching stems
• Spirally-arranged leaves (moss-like)
• Feature: Microphyll
• Adventitious roots
• Sporangium on tops of leaves
• 3 living orders:
• Ground pines
• Spike mosses
• Quillworts

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�Ground pines�

• Spirally-arranged microphyll
• Sporangia in cones or solitary; Homosporous
• Spores are flammable; “flash powder”
• Used for wreaths

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Spike-mosses

• 1 genus (Selaginella); 750 spp.
• Microphylls planated
• Sporangia in cones; Heterosporous
• Megaspores and microspores
• e.g., Resurrection fern
• Selaginella lepidophylla

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Mega

spores

Micro

spores

Selaginella tamariscina

whitetip spikemoss

Selaginella lepidophylla - rose of Jericho

Selaginella clumps in a planter

Cone with

sporangia

Cone l.s.

x40

Quillworts

• 1 genus (Isoetes); ~200 species
• Evergreen aquatics with grass-like microphylls
• Live in low-nutrient waters
• Corm-like stem with tiny amount of wood
• Heterosporous
• Absorb carbon through roots
• Unique among living plants
• Has C4 photosynthesis

Fossil Scale Trees

• Lycophytes were tree-sized
• Dominated from 370–270 million years ago; now extinct
• Source of much of world’s coal
• Monocarpic lifecycle

Laboratory Drawings

• Fern gametophyte (prothallus), prepared slide
• LABEL: Thallus, Antheridia and/or Archegonia, Rhizoids
• Fern sori, prepared slide
• LABEL: Pinna, Sorus, Sporangia, Annulus, Spores
• Selaginella, Spike-moss
• LABEL: Stem, Roots, Microphylls

Male gametophyte

Female gametophyte x100

Fern sorus x100

annulus

sporangia

archegonia

antheridia

rhizoids

Selaginella – Spike-moss x1

Additional Slides

Psilotum - Whisk fern

sporangia

enations

stem

Transition from “bryophyte”�to “pteridophyte”

Sporangium

Sporangia

Thalloid bryophyte

Fundamental differences

1. Branching in sporophyte
2. Vascular tissue
3. Independent sporophyte

Dichotomous Branching

Equal Branching

or Isotomous

Unequal Branching or

Anisotomous

Upright Branching

or Pseudomonopodial

Sporophyte

Rhizome

Vascular Patterns

Eustele

• Gymnosperm stems
• Eudicot stems
• Monocot roots

Xylem

Phloem

Leaf trace

Siphonostele

• Ferns

Leaf gap

Leaf trace

Cambium

Vascular

bundle

Protostele

• Lycophytes
• Whisk ferns
• Roots of eudicots

Monilophytes

• Eusporangiate “ferns”
• Whisk ferns, Ophioglossales, Marattiales, Horsetails
• Macroscopic, thick-walled sporangium
• Many small spores (1000s of spores)
• Only homosporous
• Leptosporangiate “ferns”
• True ferns (Polypodiidae)
• Microscopic, thin-walled sporangium
• Annulus found on sporangium
• Fewer spores (16-128 spores)
• Homosporous & heterosporous

Eusporangium

Leptosporangium

Annulus

Marattiales

• Ancient, tropical tree ferns
• Not the common tree ferns in hort. trade
• Erect short stem with large fronds
• Eusporangia abaxial on leaves
• e.g. Angiopteris, Marattia

Marattia

Grape ferns, Moonworts, and Rattlesnake ferns�Ophioglossales

• Temperate and tropical
• Small simple stem
• Simple or pinnately compound leaf
• Fertile frond with eusporangia
• e.g. Ophioglossum, Botrychium
• O. reticulatum has 1260 chromosomes
• Ribbon fern (O. pendulum) sometimes sold

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Botrychium

Ophioglossum

Ophioglossum reticulatum

Botrychium

Ophioglossum pendulum