In the foregoing cases a person is supposed to influence vegetation homoeopathically. He infects trees or plants with qualities or accidents, good or bad, resembling and derived from his own. But on the principle of homoeopathic magic the influence is mutual: the plant can infect the man just as much as the man can infect the plant. In magic, as I believe in physics, action and reaction are equal and opposite. The Cherokee Indians are adepts in practical botany of the homoeopathic sort. Thus wiry roots of the catgut plant are so tough that they can almost stop a plowshare in the furrow. Hence Cherokee women wash their heads with a decoction of the roots to make the hair strong, and Cherokee ball-players wash themselves with it to toughen their muscles. It is a Galelareese belief that if you eat a fruit which has fallen to the ground, you will yourself contract a disposition to stumble and fall; and that if you partake of something which has been forgotten (such as a sweet potato left in the pot or a banana in the fire), you will become forgetful. The Galelareese are also of opinion that if a woman were to consume two bananas growing from a single head she would give birth to twins. The Guarani Indians of South America thought that a woman would become a mother of twins if she ate a double grain of millet. In Vedic times a curious application of this principle supplied a charm by which a banished prince might be restored to his kingdom. He had to eat food cooked on a fire which was fed with wood which had grown out of the stump of a tree which had been cut down. The recuperative power manifested by such a tree would in due course be communicated through the fire to the food, and so to the prince, who ate the food which was cooked on the fire which was fed with the wood which grew out of the tree. The Sudanese think that if a house is built of the wood of thorny trees, the life of the people who dwell in that house will likewise be thorny and full of trouble.