You see, the fact that he requires so little baggage must have been a great advantage to Mr. Lichen in those early days, when he had to discover not only America but all the rest of the world map, spread out so wide and far. You can just imagine how the grains of lichen dust, the seed of the race, must have gone whirling across the world with the winds. But if a breath of wind would carry them away so easily, how could they _stay_ on a rock, these tiny lichen travellers? Especially as they have no roots? They have curious rootlike fibres which absorb food by dissolving the rock, and this dissolved rock, hardening, holds them on. The fibres of lichens that grow on granite actually sink into it by dissolving the mica and forcing their way between the other kinds of particles in the rock that they can't eat. Thus they help break it up. As we all know, little people are great eaters in proportion to their size, but it is said the lichens are the heartiest eaters in the world. They eat more mineral matter than any other plant, and all plants are eaters of minerals. Yet, you'd wonder what they do with the food they eat--most of them grow so slowly. A student of lichens watched one of them on the tiled roof of his house in France--one of the kind of lichens that look like plates of gold--and in forty years he couldn't see that it had grown a single bit, although he measured it carefully. HOW MR. LICHEN EATS UP STONES But how could such feeble creatures, as they seem to be, ever eat anything so hard as rock? Well, they couldn't if it wasn't for one thing--they understand chemistry. At least they carry with them, or know how to make, an acid, and it's this acid which enables them to dissolve the rock so that they can absorb it. The acid is in their fibres--what answer for roots. And the dissolved rock not only gives them their daily bread, but, as I said a moment ago, holds them on. This use of acid is their way of eating; chewing their food very fine, and mixing it with saliva, as all of us young people are taught to do. The first and smallest of the lichen family spread and decay into a thin film of soil. This decay makes more acid, just as decaying leaves do to-day--they learned it, no doubt, from the lichens--and this acid of decay also eats into the rock and makes more soil. (You see nature, from the start, has been helping those that help themselves, just as the old proverb has it.) Then, after the first tiny lichens--mere grains of dust that have just begun to feel the stir of life--come somewhat larger lichens which can only live where there is a little soil to begin with. These in turn die, which means a still deeper layer of soil, still more acid of decay, and so on up to larger lichens and later more ambitious plants. Then, on the soil made by these successive generations of lichens, higher types of plants--plants with true roots--get a foothold.