At one part of the face of the bank we notice a layer of a different kind. We find the roots and parts of the stems and branches of small trees embedded in the moss. There has been a wood here at one time—how long ago, we cannot tell. That layer of moss which now lies above the remains of the trees may have taken centuries to form. In many places we find more than one such layer of wood, separated as well as covered by thick layers of moss. Some of the trees have been of considerable size, too; the trunk of one found in the parish of Stenness measured about five feet in circumference, while the moss near it was thickly studded with the nuts which had fallen from it year after year. The trees whose remains have been found in our mosses include the poplar, pine, mountain ash, birch, hazel, alder, and willow. One very interesting fact is that the silver fir is also found, a tree which does not now grow in Scotland, and is not found in Scottish peat-mosses, but which is common in Norway. What curious tales those peat-mosses tell of the changes of climate which have passed over our islands! At the present day it is only in our deepest glens, as in Hoy, that we can find even small trees and bushes growing wild. Yet at one time our islands must have been well wooded, though it is only in the mosses that the remains have been preserved for us to see. The sphagnum, again, has another story to tell. It requires abundant moisture for its growth, and at present it can find this only in flat and boggy ground. It is therefore only in such places that peat is now being formed. Yet we find peat on most of our hillsides and even hilltops. This tells of a time when our climate was much wetter than it now is, and when sphagnum flourished everywhere. One more story of a different kind can be read from the peat-moss. Here and there, as at Deersound and Widewall Bay, when the tide is out, we may find peat-moss, and the remains of large trees among it, far down on the beach, many feet below the level of high water, and most of it covered to a considerable depth with the sand and gravel which form the upper beach and the land near it. This tells clearly of a gradual sinking of the land in the neighbourhood. When that moss was being formed, and when those trees were growing, the shallow bay must have been dry land. The plants and flowers which grow on our mosses are worth more than a passing glance. Let us look at some of them. The sphagnum we have already mentioned; it belongs to the class of flowerless plants. The others we shall mention are flowering plants.