Ginkgo

Already ancient when dinosaurs walked the earth, one species of tree survives virtually unchanged into the space age. Defying air pollution, disease, and insect infestation, just as it has for 150 million years, the ginkgo (Ginkgo biloba) flourishes along city sidewalks and thoroughfares in the United States and other temperate regions of the world.

To the ginkgo, 20th-century perils don't stack up to those of past millenniums. Drifting continents failed to destroy it. So did the alternating climatic cycles of tropical temperatures and frigid ice ages. Unlike its contemporaries, the ginkgo defied death. It also stopped evolving as far back as the Paleozoic era, appearing today as it did in prehistoric times.

By the time man began migrating and populating the planet, though, the ginkgo had retreated from its once-global range to the mountain forests of eastern and western China. There it thrived until the early 1700s, when explorers brought seedlings to Europe. In 1784, the ginkgo was introduced to America.

In China, ginkgo yielded its wood for carving, and the nuts of its somewhat foul-smelling fruit (that only the female tree produces) for toasted treats. However, in ginkgo's new lands, it makes the ideal ornamental and the hardiest of all street trees. When you see it, remember that you may be viewing what some scientists believe to be the living link in the evolution of ferns to trees.

Illustration: Jim Stevenson