FOSSIL PLANT LORE

Waipa Post, Volume 51, Issue 3645, 19 July 1935, Page 10

FOSSIL PLANT LORE

A MILLION-YEAR-OLD LEAF.

To find a leaf millions of years old : J is an experience few can. hope to haVe but it is one that came to Professor. Thomas A. Bonsor of Spokane, Washington, and his pupils. In a railroad cut, made a few years ago near the city, there lay, amid innumerable,imprints of other prehistoric leaves, one leaf of a ginkgo or maidenhair fern tree. Its special interest lies in the Wonderful state of preservation in which it found, its .age and the history of centuries gone,' which it helps to reveal. This little leaf was embedded in clay 30 feet beneath the surface and under 10 feet of basaltic or lava rock before it was exposed by the railroad cut. All ether fossil leaves known to have been found up to this time had been carbonated or oxidised so as to leave only an imprint, or at most a slight residue which might be blown away as dust when the rock was split open. In the case of this ginkgp, the actual leaf substance is so perfectly preserved that it could be taken' almost unbroken from its clay tomb and mounted between small pieces of glass. Except for the fact that it is now nearly black, it can hardly be distinguished from a fresh leaf. It is the property of the Spokane Public Museum. Since then two other similar leaves have been found in the same locality, and one Is now exhibited in the National Museum, Washington, D.C. • A few coniferous leaves equally well preserved have also been found. . .

The chance location undoubtedly was the reason for the excellent preservation, although the thick leathery texture and resinous nature of the leaf may have aided. The covering of lava served as a hermetical sealing for the centuries, and prevented contact with sufficient water to produce oxidation. The clay in this area contains imprints of many leaves, showing clearly that they were deposited at the bottom of a lake or arm of the sea from a nearby source. So it is impossible that the ginkgo leaf could have been carried to its resting place across any considerable body of water.

Although very ancient,.the.. ginkgo tree has come down to. the present time with the least change of any rate, at least in leaves. The specimen found is practically identical with certain forms of living species. But this unique tree remains native to modern times in only one species, and that in eastern Asia. Clear evidence shows that in other times it Was present, more or less, over practically all of North America, Europe and Asia. Today it is a prized ornamental tree in all temperate climates. If it had not had the care of temple gardeners in Asia and arboriculturists elsewhere it might have suffered total extinction. As collecting has been extensive in the area in which this ginkgo leaf was found, it is safe to assume that ginkgos were not a very conspicuous .element of the prehistoric flora, of the locality. However, each fossil leaf found is interesting and important. It tells its part of the conditions on the earth’s surface at the time it lived, and it is by signs such as this that natural scientists are able to reconstruct the history of the earth’s surface from ages past.