Thus on the theory of homoeopathic magic a person can influence vegetation either for good or for evil according to the good or the bad character of his acts or states: for example, a fruitful woman makes plants fruitful, a barren woman makes them barren. Hence this belief in the noxious and infectious nature of certain personal qualities or accidents has given rise to a number of prohibitions or rules of avoidance: people abstain from doing certain things lest they should homoeopathically infect the fruits of the earth with their own undesirable state or condition. All such customs of abstention or rules of avoidance are examples of negative magic or taboo. Thus, for example, arguing from what may be called the infectiousness of personal acts or states, the Galelareese say that you ought not to shoot with a bow and arrows under a fruit-tree, or the tree will cast its fruit even as the arrows fall to the ground; and that when you are eating water-melon you ought not to mix the pips which you spit out of your mouth with the pips which you have put aside to serve as seed; for if you do, though the pips you spat out may certainly spring up and blossom, yet the blossoms will keep falling off just as the pips fell from your mouth, and thus these pips will never bear fruit. Precisely the same train of thought leads the Bavarian peasant to believe that if he allows the graft of a fruit-tree to fall on the ground, the tree that springs from that graft will let its fruit fall untimely. When the Chams of Cochinchina are sowing their dry rice fields and desire that no shower should fall, they eat their rice dry in order to prevent rain from spoiling the crop.