Seeds which raise their cotyledons above the soil should not be planted as deep as those which do not. Large, strong seeds like corn, peas, etc., which do not lift their cotyledons above the surface, can be planted with safety at a depth of from one to four or five inches.
[Illustration: FIG. 42. To show how the bean plant gets up. Notice the curved hypocotyls pulling the seed-leaves or cotyledon out of the soil.]
[Illustration: FIG. 43. To show how the corn-plant gets out of the soil. A slender growing point pushes straight up through the soil, leaving the kernel behind.]
[Illustration: FIG. 44. To show the use of the cotyledons. These are the plants shown in tumbler 2, Fig 42, forty-eight hours after removing the cotyledons from plant _B._ Plant _B_, although first up, has been handicapped by the loss of its cotyledons.]
Seeds of carrot, celery, parsley, parsnip and egg plant are weak and rather slow in germinating. It is customary to plant them rather thickly in order that by the united strength of many seeds they may more readily come to the surface. This point should be observed also in planting seeds in heavy ground that is liable to pack and crust over before the seeds germinate.
Seed should always be sown in freshly stirred soil and may be planted by hand or with a machine.
For the home garden and the school garden, and when only small quantities of any one variety are planted, a machine is hardly desirable and hand planting is preferable.
The rows are marked out with the garden marker, or the end of a hoe or rake handle (Fig. 47), using a line or the edge of a board as a guide. The seeds are then carefully and evenly dropped in the mark or furrow.
The covering is done with the hand or a rake or hoe, and the soil is pressed over the seeds by patting it with the covering tool or walking on the row and pressing it with the feet. This pressing of the soil over the seeds is to bring the particles of soil close to each other and to the seed so that film water can climb upon them and moisten the seed sufficiently for sprouting.
A convenient way of distributing small seeds like those of turnip and cabbage, is to take a small pasteboard box or tin spice or baking-powder box, and punch a small hole in the bottom near one end or side. Through this the seeds can be sifted quite evenly.