Paleozoic Life History - The Changing Earth: Exploring Geology and Evolution - page 587

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Figure 21.33 Generalized Life History of a Seedless Vascular Plant and Gymnosperm Plant

Spore-bearing
structures
(sporangia)

Pollen

Mature fern sporophyte
(spore-bearing generation)

Male cone

Young growing fern
still attached to
gametophyte plant

Spores

Embryonic
seed

Cone scale

Egg

Female cone

Sperm

Mature gymnosperm
with cones

Tube

Mature gametophyte
plant (gamete-bearing
generation)

Seedling

Spores germinate
and grow into
gametophyte
plant

Eggs

Seed

Sperm

Gymnosperm plant

b Generalized life history of a gymnosperm plant. The mature plant
bears both male cones that produce sperm-bearing pollen grains
and female cones that contain embryonic seeds. Pollen grains are
transported to the female cones by the wind. Fertilization occurs
when the sperm moves through a moist tube growing from the
pollen grain and unites with the embryonic seed, which then grows
into a cone-bearing mature plant.

Seedless vascular plant

a Generalized life history of a seedless vascular plant. The mature
sporophyte plant produces spores, which, upon germination, grow
into small gametophyte plants that produce sperm and eggs. The
fertilized eggs grow into the spore-producing mature plant, and the
sporophyte-gametophyte life cycle begins again.

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Figure 21.34 Pennsylvanian Coal Swamp Reconstruction of a Pennsylvanian coal swamp
with its characteristic vegetation. The amphibian is Eogyrinus .