““The first forests about which anything is known were made up of the simplest kinds of plants, all of them spore-produced - horsetails, club mosses, and ferns. Relics of these primitive plants still survive today; everyone is familiar with the delicate, lacy ferns that are found in damp places in the woods, growing in the niches of rocks, spreading over the remains of fallen trees. But these plants are only miniature versions of their ancestors. During the Paleozoic era, between 280 and 425 million years ago, at about the time reptiles were evolving, ferns forty feet tall and club mosses five feet in diameter and 120 feet in height flourished in swampy lowlands between recurrent invasions of the sea. As these huge plants fell over into the water and slowly turned into peat, they retained their rich stores of solar energy, acquired through photosynthesis, which compacted first into lignite and then into coal by the growing weight of millions of years of deposits. Forest grew upon forest, and each in its turn was compressed into seams of coal beneath the surface of the ground. When we burn coal, we are using a fuel made from the sun’s energy and stored away in trees more than a quarter of a billion years ago.””
