When did Plants First Colonize the Land?

We know already that the first on Earth was probably plant and that it lived in water. Indeed, these are the very primitive algae that we have already mentioned.

You must bear in mind that these first plants did not have stems, leaves, and roots as do the plants that you might immediately think of as living today. These plants were just collections of living cells.

In rocks of Cambrian age, however, there is evidence of plants which might have lived on land. This was between 500 and 600 million year ago. But it was not until about 150 to 200 million years later that plant life became abundant on land and evidence of this can be found in rocks of the so-called Silurian and Devonian periods.

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An artist’s impression of a plant that has been found fossilized in Devonian rocks of Scotland. It lacked the true roots, leaves and seeds of modern plants.

The first plants that began to encroach the land had to live in shallow water, but they did have roots and could take in the gas carbon dioxide form the primitive atmosphere. But the first true land plants were a group which are called psilophytes. They still had to live in damp places, however, and they do not seem to be directly related to any plants living today.

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The modern club moss and the fossilized fragment of a lepidodendron shown here belong to the same group of primitive plants.

The first trees appeared in the Devonian, although they were not much like the tress that you will be familiar with in a modern country landscape. For one thing these trees, with the group name of lepidodendrons, did not produce flowers, and in fact it was not until a mere 135 million years ago that the first flowering plants became abundant.

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These horsetails, fens, seed ferns, and tree ferns can be found fossilized in rocks of Carboniferous age.

Modern examples of very primitive land plants are the ferns and mosses. About 350 million years ago, however, land plants became so abundant that their remains have left us with the deposits of coal which are so important to our industries and help to warm many of our homes.

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