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Rh men bid one moisten the seed in nitre for a night and sow it in dry ground the next day. To make lentils vigorous they plant the seeds in dung ; to make chick-peas large they bid one moisten the seed while still in the pods, before sowing. Also the time of sowing makes differences which conduce to digestibility and harmlessness : thus, if one sows vetches in spring, they become quite harmless and are not indigestible like those sown in autumn.

Again in pot-herbs change is produced by cultivation; for instance, they say that, if celery seed is trodden and rolled in after sowing, it comes up curly it also varies from change of soil, like other things. Such variations are common to all; we must now consider whether a tree, like animals, becomes unproductive from mutilation or removal of a part. At all events it does not appear that division is an injury, as it were, which affects the amount of fruit produced either the whole tree perishes, or else, if it survives, it bears fruit. Old age however is a cause which in all plants puts an end to life. ….

It would seem more surprising if the following changes occurred in animals naturally and frequently; some animals do indeed seem to change according to the seasons, for instance, the hawk the hoopoe and other similar birds. So also changes in the nature of the ground produce changes in animals, for instance, the water-snake changes into a viper, if the marshes

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