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plant contains potentially both root and stem。 Hence it is from this
source that issues that continued growth when one part is renewed
and the other grows old； it is practically a case of longevity。 The
taking of slips furnishes a similar instance； for we might say that；
in a way； when we take a slip the same thing happens； the shoot cut
off is part of the plant。 Thus in taking slips this perpetuation of
life occurs though their connexion with the plant is severed； but in
the former case it is the continuity that is operative。 The reason
is that the life principle potentially belonging to them is present in
every part。
Identical phenomena are found both in plants and in animals。 For
in animals the males are； in general； the longer…lived。 They have
their upper parts larger than the lower （the male is more of the dwarf
type of build than the female）； and it is in the upper part that
warmth resides； in the lower cold。 In plants also those with great
heads are longer…lived； and such are those that are not annual but
of the tree…type； for the roots are the head and upper part of a
plant； and among the annuals growth occurs in the direction of their
lower parts and the fruit。
These matters however will be specially investigated in the work
On Plants。 But this is our account of the reasons for the duration
of life and for short life in animals。 It remains for us to discuss
youth and age； and life and death。 To come to a definite understanding
about these matters would complete our course of study on animals。
…THE END…
。