1. Plants

2. Devonian Period
(517-354 MYA)

3. Plant Proliferation
Plants began spreading beyond the wetlands
during the Devonian, with new types developing
that could survive on dry land. Toward the end of
the Devonian the first forests arose as stemmed
plants evolved strong, woody structures capable of
supporting raised branches and leaves. Some
Devonian trees are known to have grown 100 feet
(30 meters) tall. By the end of the period the first
ferns, horsetails, and seed plants had also
appeared.

4. Plants during the Devonian Period
The genus Prototaxites describes terrestrial
organisms known only from fossils dating from
the Silurian and Devonian, approximately 420
to 370 million years ago. Prototaxites formed
large trunk-like structures up to 1 metre (3 ft)
wide, reaching 8 metres (26 ft) in height, made
up of interwoven tubes just 50 micrometres
(0.0020 in) in diameter. Whilst traditionally
very difficult to assign to an extant group of
organisms, current opinion is converging to a
fungal placement for the genus. It might have
had an algal symbiont, which would make it a
lichen rather than a fungus in the strict sense.
An opposing view has been presented that
Prototaxites was not a fungus but consisted of
enrolled liverwort mats with associated
cyanobacteria and fungal tubular elements.

5. Plants during the Devonian Period
Archaeopteris is an extinct genus of tree-like
plants with fern-like leaves

6. Carboniferous Period
(354-290 MYA)

7. Description

8. Plants during the Carboniferous
Period
The Equisetales is an order of
pteridophytes with only one
living genus Equisetum
(horsetails), of the family
Equisetaceae
Fossil leaves and branches of the species
Sphenophyllum miravallis

9. Plants during the Carboniferous
Period
The order Polypodiales encompasses the
major lineages of polypod ferns, which
comprise more than 80% of today's fern
species. They are found in many parts of the
world including tropical, semitropical and
temperate areas.
The Medullosales is an order of
pteridospermous seed plants characterised by
large radiospermic ovules with a vascularised
nucellus, complex pollen-organs, stems and
rachises with a dissected stele, and frond-like
leaves. Their nearest still-living relatives are
probably the cycads.

10. Plants during the Carboniferous
Period
The Lycopodiopsida are a class of
plants often loosely grouped as the
fern allies. Traditionally, the group
included not only the clubmosses and
firmosses, but also the spikemosses
(Selaginella and relatives) and the
quillworts (Isoetes and relatives).
Lepidodendrales (from Gr. "scale tree") were
primitive, vascular, arborescent (tree-like)
plants related to the lycopsids (club mosses).

11. Plants during the Carboniferous
Period
Cordaitales are an extinct order of woody
plants that may have been early conifers, or
which may have given rise to the conifers
(Pinophyta), ginkgos (Ginkgophyta) and
cycads (Cycadophyta). They had cone-like
reproductive structures reminiscent of those
of modern conifers.
Cycads are seed plants typically characterized
by a stout and woody (ligneous) trunk with a
crown of large, hard and stiff, evergreen
leaves.

12. Plants during the Carboniferous
Period
Lepidodendron — known as scale trees
— were a now extinct genus of primitive,
vascular, arborescent (tree-like) plant
related to the lycopsids (club mosses).
They were part of the coal forest flora.
They sometimes reached heights of over
30 metres (100 ft), and the trunks were
often over 1 m (3.3 ft) in diameter, and
thrived during the Carboniferous Period

13. Permian Period
(290-248 MYA)

14. Description
The Permian period, which ended in the largest
mass extinction the Earth has ever known, began
about 299 million years ago. The emerging
supercontinent of Pangaea presented severe
extremes of climate and environment due to its
vast size. The south was cold and arid, with much
of the region frozen under ice caps. Northern
areas suffered increasingly from intense heat and
great seasonal fluctuations between wet and dry
conditions. The lush swamp forests of the
Carboniferous were gradually replaced by conifers,
seed ferns, and other drought-resistant plants.

15. Description
The Permian, however, represented the last gasp
for much early prehistoric life. The period, and the
Paleozoic era, came to a calamitous close 251
million years ago, marking a biological dividing line
that few animals crossed. The Permian extinction
—the worst extinction event in the planet's history
—is estimated to have wiped out more than 90
percent of all marine species and 70 percent of
land animals.

16. Description
Various theories seek to explain this mass
extinction. Some scientists think a series of
volcanic eruptions pumped so much debris into the
atmosphere that the sun was blocked out, causing
a significant drop in temperature and preventing
plant photosynthesis, which in turn caused food
chains to collapse.

17. Description
Other scientists point to global climate change,
citing evidence for a period of sudden warming
and cooling. These rapid extremes of conditions
may have meant species were unable to adjust.
Other theories include a catastrophic release of
methane gas stored under the seabed, triggered
by earthquakes or global warming, or a massive
asteroid impact.

18. Plants during the Permian Period
Sigillaria is a genus of extinct, spore-bearing,
arborescent (tree-like) plants

19. Plants during the Permian Period
Glossopteris, (meaning "tongue",
because the leaves were tongueshaped) is the largest and bestknown genus of the extinct order
of seed ferns known as
Glossopteridales
Ginkgo

20. Mass Extinction