Mean atmospheric O2
Geologic Time Scale
Thousands of individual pre-vascular, axial, free-sporing land plants of the genus Aglaophyton populate an Early Devonian bay (in this case the remains of an already ancient crater) 415 million years ago.
Standing about 10 inches tall, Aglaophyton consisted of simple, branching stalks topped with sporangia. The sporangia, here colored red, held spores for reproduction. (Note that the colors are only a guess as these early terrestrial plants long ago became extinct during the Middle Devonian.) Instead of roots, these simple plants had horizontal stems with fibrous rhizoids that may have drawn moisture and nutrients from the soil with the aid of mycorrhizal fungi.
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