But why are there no trees on the moors, you may ask! It cannot be that they are on too high a level for trees to grow, for some even higher hills are clothed with them. The truth is that probably long ago there were trees on the moors, but men cut them down foolishly without having planted young ones between the old ones, which would have replaced them. When once all the trees are cut down on a hillside, it is very difficult for young ones to get a start again, because everything which makes it hard for ordinary small plants to grow hinders the young trees, and the worst of all these things is the strong wind, which can rush unchecked over the bare moor. A strong wind is more powerful than a young tree, and kills it. The plantations of young trees which are to be found on the moorland have to be started on the sheltered side, and require much care and attention. You will notice that the trees which do grow there are those which are specially fitted for a hard life, such as the pine, larch, and birch. Another feature of the moorland, and one which cannot long escape our notice if we walk about moors at all, is the number of patches of wet moss which shake and tremble beneath our feet, and may form great stretches of bog-land. Sometimes this is so soft that it gives way altogether, and one may be knee-deep in moss and water, where it looked firm enough to the eye. You will find this bog moss grows in a peculiar way, the fresh green branches growing up and up, while below lie the half dead older stems, which are partly preserved by the peaty acids. These layers of moss collect for many years, till very thick masses of peat-bog may be formed. Among the bog-moss you will often find the sundew and butterwort (~see~ pp. 114-15), which are two of our chief insect-eating plants. They love the boggy moorland, or a damp spot beside a little moorland stream. There is a curious thing you may have the chance of seeing in a wet moor. If you find a stream dripping over a ledge some little distance on to the rocks below, you may see how thick and beautifully green are the patches of moss growing beneath its spray. If the stream has passed over much limestone (and is therefore carrying some in solution), you may see below the living moss much dead moss just covered with a thin coating of lime. Below this is more moss, which has been made quite hard with the lime, and is brittle and snaps if you try to bend it, while below this again is a hard, compact mass of stone which is made from the stony stems of the moss crushed together by the weight above them and filled in with more deposited lime. In some places great masses of rock are formed in this way. You have here, acted before your eyes, a piece of the history not only of the living and dying plants of to-day, but of the building of rocks, which may some day help in the building of mountains. [Illustration: PLATE V. WATER PLANTS GROWING PARTLY BELOW AND PARTLY ABOVE THE SURFACE OF THE WATER]