On Youth And Old Age, On Life And Death, On Breathing   

a number of trees can be derived from one single source. A separate

account will be given of the reason why some plants cannot live when

divided, while others can be propagated by the taking of slips. In

this respect, however, plants and insects are alike.

It is true that the nutritive soul, in beings possessing it, while

actually single must be potentially plural. And it is too with the

principle of sensation, for evidently the divided segments of these

animals have sensation. They are unable, however, to preserve their

constitution, as plants can, not possessing the organs on which the

continuance of life depends, for some lack the means for seizing,

others for receiving their food; or again they may be destitute of

other organs as well.

Divisible animals are like a number of animals grown together, but

animals of superior construction behave differently because their

constitution is a unity of the highest possible kind. Hence some of

the organs on division display slight sensitiveness because they

retain some psychical susceptibility; the animals continue to move

after the vitals have been abstracted: tortoises, for example, do so

even after the heart has been removed.



3



The same phenomenon is evident both in plants and in animals, and in

plants we note it both in their propagation by seed and in grafts

and cuttings. Genesis from seeds always starts from the middle. All

seeds are bivalvular, and the place of junction is situated at the

point of attachment (to the plant), an intermediate part belonging

to both halves. It is from this part that both root and stem of

growing things emerge; the starting-point is in a central position

between them. In the case of grafts and cuttings this is

particularly true of the buds; for the bud is in a way the

starting-point of the branch, but at the same time it is in a