The seeds of cucumber, melon, etc., are better, at any rate, when four
of five years old than when fresh; and we have well authenticated
instances of seeds retaining their vitality much longer than this.
There is _no_ fixed period during which seeds will keep. There is no
reason to suppose that they would lose their vitality in any
assignable number of years _if the proper conditions were observed_.
De Candolle says that M. Gerardin raised kidney beans, obtained from
Tournefort’s herbarium, which were at least a hundred years old; but
beans left to the chances of the atmosphere are not good the second
year, and hardly worth planting in the third. Professor Lindley raised
raspberry plants from seed not less than sixteen or seventeen hundred
years old. Multitudes of other instances might be given. In reply to
the first question, it may, then, be said, that the length of time
through which seeds will keep depends upon the method of preserving
them.
We do not suppose it to be essential to inclose apple, pear, and
quince seeds in earth for the purpose of preserving their vitality
during a single winter. But if exposed to the air, the rind becomes so
hard and rigid as to make germination very difficult from mere
mechanical reasons. The moisture of the soil keeps the covering in a
tender state, and it is easily ruptured by the expansion of the seed.
The shell of peach, plum, and other stone-fruit seeds would form, if
left to dry and harden, a yet more hopeless prison. If kept for two
years, the most stone-fruit pips, it is to be presumed, would not
germinate. Some, however, would have vigor enough to grow even then.
We have forgotten who it was, but believe it to have been a reliable
person, recently mentioned the fact, that a peach or apricot stone was
for several years kept as a child’s play-thing; but upon being
planted, grew, and is now a healthy tree. Such cases are, however,
rare.
The intercourse between Great Britain and her distant colonies, and
the various expeditions fitted out from her shores for purposes of
botanical research and for the acquisition of new plants from distant
regions, have made the subject of seed-saving at sea a matter of much
experiment.
In general, the conditions of preservation are three; a low
temperature, dryness, and exclusion of air. But it often happens, that
all these cannot be had, and then a choice must be made between them.
Heat and moisture will either germinate the seeds or corrupt them. In
long voyages, and in warm regions, _moisture contained in the seed_,
if in a close bottle, is sufficient to destroy the seed. Glass bottles
have therefore been rejected. Seeds for long voyages, or for long
preservation, are thoroughly ripened and thoroughly dried; but dried
without raising the _temperature_ of the air, as this would impair
their vitality. They are then wrapped in coarse paper, and put,
loosely, in a coarse canvas bag, and hung up in a cool and airy place.
In this way seeds will be as nearly secure from heat and
moisture—their two worst enemies—as may be. It is probable that some
seeds have but a short period of vitality under any circumstances of
preservation. Seeds containing much oil, are peculiarly liable to
spoil. Lindley suggests that the oil becomes rancid.
The preservation of seeds from one season to another, for home use, is
not difficult, and may be described in three sentences: ripen them
well, dry them thoroughly, and keep them aired and cool.