In every case the testers should be kept at a temperature of about seventy degrees or about that of the living room.

HOW THE SEEDS COME UP

Plant a few seeds of corn, beans and garden peas in boxes or tumblers each day for several days in succession.  Then put seeds of corn, beans and garden peas to soak.  After these have soaked a few hours, examine them to find out how the seed is constructed.  Note first the general shape of the seeds and the scar (Fig. 41-4) on one side as in the bean or pea and at one end or on one edge in the corn.  This scar, also called hilum, is where the seed was attached to the seed vessel.

Cut into the bean and pea, they will be found to be protected by a tough skin or coat.  Within this the contents of the seed are divided into two bodies of equal size lying close to each other and called seed leaves or cotyledons (Fig. 41-5).  Between them near one end or one side will be found a pair of very small white leaves and a little round pointed projection.  The part bearing the tiny leaves was formerly, and is sometimes now, called the plumule, but is generally called the epicotyl, because it grows above or upon the cotyledons.  The round pointed projection was formerly called the radicle, but is now spoken of as the hypocotyl, because it grows below or under the cotyledons.

Examine a dry kernel of corn and notice that on one side there is a slight oval-shaped depression (Fig. 41-1).  Now take a soaked kernel and cut it in two pieces making the cut lengthwise from the top of the kernel through the centre of the oval depression and examine the cut surface.  A more or less triangular-shaped body will be found on the concave side of the kernel (see Figs. 41-2 and 41-3).  This is the one cotyledon of the corn.  Besides this will be found quite a mass of starchy material packed in the coverings of the kernel and in close contact with one side of the cotyledon.  This is sometimes called the endosperm.

Within the cotyledon will be found a little growing shoot pointed toward the top of the kernel.  This is the epicotyl, and another growing tip pointed toward the lower end of the kernel; this is the hypocotyl or the part which penetrates the soil and forms roots.

Now examine the seeds that were planted in succession.  Some will be just starting a growing point down into the soil.  Some of them have probably come up and others are at intermediate stages.

How did the bean get up?

After sending down a root the hypocotyl began to develop into a strong stem which crooked itself until it reached the surface of the soil and then pulled the cotyledons or seed-leaves after it (Fig. 42).  These turn green and after a time shrink and fall off.

The pea cotyledons were left down in the soil, the epicotyl alone pushing up to the surface.  The corn pushed a slender growing point to the surface leaving the cotyledon and endosperm behind in the soil but still attached to the little plant (Fig. 43).