Life on Earth
Kingdom Plantae
Part II
Rhyniophyta and
Lycopodiophyta
Cooksonia
Introduction
• Sporophyte generation (2N) is the
photosynthetic, conspicuous generation
• All members have evolved specialized
tissues for water (XYLEM) and food
(PHLOEM) conduction
• Groups continue to become better
adapted to the terrestrial environment
Evolutionary Lines
PLANT KINGDOM
“bryophytes”
“vascular
plants”
“green algae”
Evolution of Non-Seed, Vascular Plants
Early Devonian Landscape
(about 400 million years ago)
Reconstructed Early Devonian
Landscape
Aglaophyton
Psilophyton
early lycophytes
Zosterophyllum
Cooksonia
Phylum: Rhyniophyta
• Known from fossils more
than 400 million years old
(all extinct today)
• Sporophytes had no roots
or leaves
• Sporangia produced only
one kind of spore
(homosporous)
• Example:
– Rhynia (found in chert
beds in England)
Phylum: Lycophyta
• Plants with true roots and
microphyllous leaves
• Some species produce compacted
sporophylls into a cone or strobilus
• Some genera are homosporous
(Lycopodium and Huperzia) others are
heterosporous (Selaginella and
Isoetes)
Heterospory vs. Homospory
HOMOSPOROUS
PLANTS
spores
gametophyte generation
with archegonia AND
antheridia (monoecious)
or
female gametophyte
with archegonia
dioecious
gametophytes
male gametophyte
with antheridia
microspores
megaspores
HETEROSPOROUS
PLANTS
Lycopodium
• Common in New England
and the Great Lakes
Region
• Often used for Christmas
decorations (evergreen)
• Spores were once used
as photographic flash
powder
Lycopodium (strobili)
Selaginella
• Species are heterosporous with
microsporangia and
megasporangia
• Megaspores develop into female
gametophytes
• Microspores develop into male
gametophytes
• Large group with tropical,
temperate and desert species
Selaginella rupestris
Selaginella with strobili
Selaginella striboli
megasporangium
microsporangium
Selaginella strobilus
Selaginella (sporangia)
megasporangium
microsporangium
Selaginella lepidophylla
Isoetes
• Commonly known as
“quillworts”
• Each microphyllous leaf is a
sporophyll, either a
microsporophyll or a
megasporophyll
(heterosporous)
• Stem is a fleshy “corm”
• Often grow at the margins of
ponds and lakes
Isoetes
Isoetes microsporangium
Isoetes
Isoetes melanopoda (Nebraska)
Lepidodendron
• Known as the fossil
“scale tress”
• Common forest
giant of the
Carboniferous
Period
• Helped to form
present day coal
deposits
Carboniferous Forest Reconstruction
Lepidodendron
Base of Lepidodendron (Stigmaria)