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Seedless Vascular Plants
(continued invasion of land)
Psilotophyta
Lycophyta —> [Lycopodiaceae
Selaginellaceae]
Sphenophyta… Equisetopsida… Equisetum (horse tails)
Pterophyta (ferns)
• As a photosynthetic organism, the higher you get, the closer you are to
photosynthesizing and you’re able to transfer water up to your
photosynthetic branches
...
Many
examples of fossils that can do this
...
The angiosperms- flowering plants
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Ferns still remain a relatively important part
...
It has to get water from some place
...
Soil is a biotic outcome- made by
living organisms
...
This
is the important aspect associated with this
...

• If you see any plant in its natural environment, the major part of its biomass is
below the surface i
...
roots
...
very poorly developed root
structure
...
The branching is known as dichotomous
branching
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If
you tae a cross section of the stem- it has whats known as a protostele
form
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• Has an alteration of generation
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The gametophyte is ACDC so you have male and female
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Lycophyta
• Nowadays only grows up to a height of 10cm
...
Pretty
common in bushes
...

• Grows effectively on a surface and can also adopt a sterile structure
...

• The lycophyta has been separated into two families, [Lycopodiaceae
and Selaginellaceae]
• Lycopodiaceae is known as a homospore- they have single spores
...
No sort of selective advantage- What makes in
interesting in terms of evolution is that its heterosporic trait was captured
by the gymnosperms and the angiosperms
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Equisetopsida or Equisetum
• They tend to be quite beautiful and they tend to grow in dry areas and are
capable of surviving in dry conditions
...
Whats interesting is that they have silicaceous
walls
...
They’re
edible - have a name scouring rush- due to the glass walls can use them
to furnish things because they’re so hard on the outside
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Have a motile sperm
associated with it which can swim
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One of the things thats associated with all of these groups is the presence of
stomates
...

Pterophyta (ferns)
• Ferns are presently a fairly dominant group and are sometimes trees as well
...
A lot of detail
associated with the leaf structures
...
In the case of equisetum you get a
thin strand of xylem going through the wall
...
So from the structure of the equisetum to the fern whats
happening is that you’re building a greater and greater complexity of the
vascular system
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• With the psilotum- the vascular system is quite simple
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• In order to grow high and capture the light - need something that is flat broad
and wide but in order to do that need a supply of water in order to supply
water to every cell in that flat broad leaf
...
This
complexity of the eustele is associated with ferns and is still present
today
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