one year old,
75 per cent when two years old, and 70 per cent when three years
old--the per cent of vitality diminishing with increase of years. The
average length of life of the seeds of cultivated plants is short: for
example, the tomato lives four years; corn, two years; the onion, two
years; the radish, five years. The cucumber seed may retain life after
ten years; but the seeds of this plant too lose their vitality with an
increase in years.

It is important when buying seeds to test them for purity and vitality.
Dealers who are not honest often sell old seeds, although they know that
seeds decrease in value with age. Sometimes, however, to cloak
dishonesty they mix some new seeds with the old, or bleach old and
yellow seeds in order to make them resemble fresh ones.

It is important, therefore, that all seeds bought of dealers should be
thoroughly examined and tested; for if they do not grow, we not only pay
for that which is useless but we are also in great danger of producing
so few plants in our fields that we shall not get full use of the land,
and thus we may suffer a more serious loss than merely paying for a few
dead seeds. It will therefore be both interesting and profitable to
learn how to test the vitality of seeds.

To test vitality plant one hundred seeds in a pot of earth or in damp
sand, or place them between moist pieces of flannel, and take care to
keep them moist and warm. Count those that germinate and thus determine
the percentage of vitality. Germinating between flannel is much quicker
than planting in earth. Care should be used to keep mice away from
germinating seeds. (See Fig. 61.)

[Illustration: FIG. 61. A SEED-GERMINATOR
Consisting of two soup plates, some sand, and a piece of cloth]

Sometimes the appearance of a package will show whether the seed has
been kept in stock a long time. It is, however, much more difficult to
find out whether the seeds are pure. You can of course easily
distinguish seeds that differ much from those you wish to plant, but
often certain weed seeds are so nearly like certain crop seeds as not to
be easily recognized by the eye. Thus the dodder or "love vine," which
so often ruins the clover crop, has seeds closely resembling clover
seeds. The chess, or cheat, has seeds so nearly like oats that only a
close observer can tell them apart. However, if you watch the seeds that
you buy, and study the appearance of crop seeds, you may become expert
in recognizin