These, when once
formed, may grow out into twigs, with leaves and flowers and roots. They
may even be separated from the plants and used as cuttings to reproduce
the whole. Hence we may conclude that all tissues, which possess the
power of producing adventitious buds, must conceal in a latent state,
all the numerous characters required for the full development of the
whole individual.
Adventitious buds may proceed from specialized cells, as on the margin
of the leaves of _Bryophyllum calycinum_; or from the cells of special
tissues, as in the epidermis of the begonias; or they may be provoked by
wounds in nearly every part of the plant, provided it be able to heal
the wound by swelling tissues or [219] callus. The best instance is
afforded by elms and by the horse-chestnut. If the whole tree is hewn
down the trunk tries to repair the injury by producing small
granulations of tissue between the wood and the bark, which gradually
coalesce while becoming larger. From this new ring of living matter
innumerable buds arise, that expand into leafy branches, showing clearly
that the old trunk possesses, in a latent state, all the qualities of
the whole crown. Indeed, such injured stumps may be used for the
production of copses and hedges.
All the hitherto recorded cases of latency have this in common, that
they may become active during the life-time of any given individual
once, or oftener.
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