If you notice the effect of a heavy shower of rain on a road or bare earth, you will see how soon tiny valleys and cañons and beds of streamlets are cut out. But on the green fields beside the road, there is no change in the surface at all! It seems to be quite unaffected by the heaviest storm of rain. CHAPTER XIV ON VEGETABLE DEMONS Animals and grass--Travellers in the elephant grass--Enemies in Britain--Cactus _versus_ rats and wild asses--Angora kids _v._ acacia--The Wait-a-bit thorn--Palm roots and snails--Wild yam _v._ pig--Larch _v._ goat--Portuguese and English gorse--Hawthorn _v._ rabbits--Briers, brambles, and barberry--The bramble loop and sick children or ailing cows--Briers of the wilderness--Theophrastus and Phrygian goats--Carline near the Pyramids--Calthrops--Tragacanth--Hollies and their ingenious contrivances--How thorns and spines are formed--Tastes of animals. By far the greater number of wild animals live by eating vegetables. If one thinks of the elephant's trunk, the teeth of a hippopotamus, or even of the jaws and lips of mice, rats, and voles, the thoroughly practical character and efficiency of their weapons become the more astonishing the more one reflects upon them. Yet the defences adopted by plants are just as wonderful, and are often most ingenious. It seems at first remarkable that the most usual food of animals, grass, should be apparently unprotected. It is upon grass that the great herds of bison, of buffalo, of antelope, and guanaco, are or were supported. Yet grass is so wonderfully reproductive, produces such enormous quantities of buds and foliage, and grows in such luxuriance, that there is no fear of its being killed out. There are many places in the world where vegetation defies the attacks of the animal world. Neither man nor elephant can live comfortably in the thick jungles of West Africa and the great forests of Brazil. Nor can either man or elephant utilize great tracts of country in Central Africa which are covered by the Elephant Grass. For, perhaps, four or five hours the weary caravan plods on through a sort of burrow, two feet wide, made in this gigantic grass. The stems are ten feet or more in height, and nearly meet overhead. There is nothing whatever to be seen except the narrow path. The atmosphere is stifling and hot. To cut a new road a few hundred yards long through it involves hours of labour. It is only when there has been a long drought that it is possible to set fire to the Elephant Grass, and then for a very short time the young growing shoots can be grazed. But no cattle can break through when it is fully grown. The very exuberance of vegetation in such cases prevents any harm.