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Land plants have existed for about 425 million years. Early land plants reproduced by spores like their aquatic counterparts. Marine organisms can easily scatter copies of themselves to float away and grow elsewhere. Land plants soon found it advantageous to protect their copies from drying out and other abuses by enclosing them in a case, the seed. Early seed bearing plants, like the ginkgo, and conifers (such as pines and firs), did not produce flowers.The earliest fossil of an angiosperm, or flowering plant, Archaefructus liaoningensis, is dated to about 125 million years BP. Pollen, considered directly linked to flower development, has been found in the fossil record perhaps as long ago as 130 million years.While there is only hard evidence of such flowers existing about 130 million years ago, there is some circumstantial evidence that they may have existed 250 million years ago. A chemical used by plants to defend their flowers, oleanane, has been detected in fossil plants that old, including gigantopterids, which evolved at that time and bear many of the traits of modern, flowering plants, though they are not known to be flowering plants themselves, because only their stems and prickles have been found preserved in detail; one of the earliest examples of petrification.