We could hardly leave the Carboniferous time without at least brief mention of the ginkgo tree (Figure 109), or, as some call it, the maidenhair tree. From the upper strata of the Carboniferous it is common, as it is in practically all subsequent fossil accumulations down to the most recent. And yet the tree has never been found wild, although its frequency in temple gardens in China and Japan, always as a cultivated tree, suggests that its disappearance as a wild plant must have come since the priests began preserving it, which can be only a matter of a few thousand years at most. In other words, we have just missed seeing in the ginkgo what has so many times happened to these very ancient types of vegetation, namely, their final extinction. This must have occurred within historic times, and, judging by its frequent use as a temple tree in eastern Asia, that region was its last outpost after its long journey from the dim past. Thousands of other ancient plants have completely disappeared, and one cycad from New South Wales is at this moment putting up a losing fight against modern competitors, but in the ginkgo tree the actual twilight and extinction of its wild existence has missed observations by modern plant geographers by only a brief period. It is almost as though we had waited all our life to see some great event and then missed it by a few moments. Fortunately the tree is now common in cultivation, and not the least interesting feature of it is the fact that its male fertilizing cell retains its power of movement, which dates back to its early associates. Among modern flowering plants only the ginkgo and the relatives of the sago palm or cycads retain this relic of an overwhelmingly cryptogamous ancestry. The end of the Carboniferous or coal-forming ages was marked by great changes in the earth’s surface, some of them cataclysmic in their effects. What they were in detail is described in the volume on geology and need not be repeated here. What happened to the development of the plant kingdom after this will be considered in the next section of this chapter. 4. MORE RECENT ANCESTORS OF OUR MODERN FLORA