Nucleic multicellular photosynthetic organisms lived in freshwater communities on land as long ago as a thousand million years, and their terrestrial descendants are known from the late PreCambrian 850 million years ago. Embryophyte land plants are known from the mid Ordovician, and land plant structures such as roots and leaves are recognisable in mid Devonian fossils. Seeds seem to have evolved by the late Devonian.
The earliest known plant group is the Archaeplastida, which were autotrophic. Listing just the surviving descendants, which evolved in turn, we have the Red Algae, the Chlorophyte Green Algae, the Charophyte Green Algae, and then the Embryophyta or land plants. The earliest embryophytes were the Liverworts, followed by the Hornworts, and the Mosses. Then we have the Vascular Plants, the Lycophytes and Ferns, followed by the Spermatophytes or seed plants, of which the non-flowering types are the Gnetophytes, Conifers, Ginkgos, and Cycads. The last four are also referred to as Gymnosperms, because their seeds are unprotected by an ovary or fruit. The seeds develop either on the surface of scales or leaves, which are often modified to form cones, or are solitary as in the yew and ginkgo. This completes the evolutionary order of the non-flowering plants. The final group to evolve was the Magnoliophyta (Angiosperms) or flowering plants, whose seeds and ovules are enclosed within an ovary or fruit, and which are on a separate list.
