The oldest known land inhabiting plants belong to
Lycopsida
Sphenopsida
Psilopsida
Pteropsida
Psilopsida:
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Psilopsida are the oldest known land inhabiting plants. They are rootless, however, rhizoids are present. These species are homosporous i.e. they produce only one kind of spores. Homosporous. Most of them are present as fossils. E.g. Psilotum