ALGAE (other than prokaryotes and protists) Nearly all aquatic. Most are soft and not easily preserved as fossils; but a few shallow marine forms (which are often abundant in shelf environments) have calcium carbonate in or on their cell walls, and the freshwater Characeae (Silurian to Present) may have the whole plant, or just the outer layer of the egg cell, calcified.
BRYOPHYTA (Devonian to Present) Mosses and liverworts.
VASCULAR PLANTS Land plants with woody tissue.
PTERIDOPHYTA (Silurian to Present)
Plants that produce spores asexually in alternate generations; the spores then grow into very different small plants, which reproduce sexually to form a new generation of larger plants.
PSILOPHYTES (Upper Silurian to Upper Devonian) The earliest known land plants, with a simple organization.
LYCOPODS (Lower Devonian to Present)
Plants with simple leaves borne singly. Include varied and large forms in the Carboniferous (e.g. Lepidodendron). At present fewer and smaller (the club mosses).
CALAMITES (Devonian to Present)
Plants with simple leaves in circlets. Reached climax in the Carboniferous (e.g. Calamites); now represented only by the horsetails.
FERNS (Devonian to Present)
Plants with leaves elaborately branched. Still important today. GYMNOSPERMAE (Devonian to Present)
Plants producing seeds fertilized by pollen carried by wind or insects.
CONIFERS (Carboniferous to Present)
Plants with simple needle leaves. Abundant in the Mesozoic and still important.
CYCADS (Permian to Present)
Plants with leaves like feather-palms. Abundant in the Mesozoic, less common now.
The Gymnosperms also include the Pteridosperms (e.g. Glos-sopteris) the Cordaites and the Ginkgos.
ANGIOSPERMAE (Cretaceous to Present)
Flowering plants, with the young seed enclosed in an ovary, and the pollen received on a special organ, the stigma. May be preserved as wood, leaves, seeds, fruit and pollen.
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