For large seeds take two plates (see Fig. 39) and a piece of cloth as wide as the bottom of the plate and twice as long. Count out fifty or one hundred seeds from a package, wet the cloth and wring it out.
Place one end of the cloth on the plate, place the seeds on the cloth and fold the other end of the cloth over them. On a slip of paper mark the number of seeds and date, and place on the edge of the plate. Now cover the whole with another plate, or with a pane of gla.s.s to keep from drying. Set the plate of seeds in a warm room and examine occasionally for several days. If the cloth tends to dry, moisten it from time to time. As the seeds sprout take them out and keep a record of them. Or leave them in the plate and after four or five days count those that have sprouted. This will give the proportion of good seeds in the packages.
For small seeds fold the cloth first and place the seeds on top of it.
Another good tester for small seeds is made by running about an inch of freshly mixed plaster of Paris into a small dish or pan and moulding flat cavities in the surface by setting bottles into it. The dish or pan and bottles should be slightly greased to prevent the plaster sticking to them. When the cast has hardened it should be turned out of the mould and set in a large dish or pan. One hundred small seeds are then counted out and put into one of the cavities, others are put into the other cavities. Water is then poured into the pan till it rises half way up the side of the plaster cast or porous saucer. The whole thing is then covered to keep in the moisture (Fig.
40).
Another method is to get boxes of finely pulverized sand or soil and carefully plant in it fifty or one hundred seeds of each kind to be tested. Then by counting those that come up, the proportion of good seeds can easily be found.
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 ma.s.s 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).
USE OF COTYLEDONS AND ENDOSPERM
=Experiment.=--Plant some beans in a pot or box of soil and as soon as they come up cut the seed-leaves from some of them and watch their growth for several days. It will soon be seen that the plants on which the seed-leaves were left increase in size much more rapidly than those from which the seed-leaves were removed (see Figs. 43 and 44).
Sprout some corn in the seed tester. When the seedlings are two or three inches long, get a wide-mouthed bottle or a tumbler of water and a piece of pasteboard large enough to cover the top. Cut a slit about an eighth of an inch wide from the margin to the centre of the pasteboard disk. Take one of the seedlings, insert it in the slit, with the kernel under the pasteboard so that it just touches the water. Take another seedling of the same size, carefully remove the kernel from it without injuring the root, and place this seedling in the slit beside the first one (Fig. 45). Watch the growth of these two seedlings for a few days. Repeat this with sprouted peas. In each case it will be found that the removal of the seed-leaves or the kernel checks the growth of the seedling. Therefore, it must be that the seed-leaves which appear above ground, as in the case of the bean, or the kernel of the corn which remains below the surface of the soil, furnish the little plant with food until its roots have grown strong enough to take sufficient food from the soil.
[Ill.u.s.tration: FIG. 39.
A seed-tester, consisting of two plates and a moist cloth.]
[Ill.u.s.tration: FIG. 40.--A SEED-TESTER.
A plaster cast with cavities in the surface for small seeds.]
[Ill.u.s.tration: FIG. 41.
1. Corn-kernel showing depression at _z_. 2. Section of same after soaking. 3. Corn-kernel after germination has begun. The seed-coat _a_ has been partly removed. 4. Bean showing scar or hilum at _h_. 5. The same, split open. 6. Bean with one cotyledon removed, after sprouting had begun. _a_, Seed-coat; _b_, cotyledon; _c_, epicotyl; _d_, hypocotyl; _e_, endosperm. (Drawings by M.E. Feltham.)]
CHAPTER X
SEED PLANTING
HOW DEEP SHOULD SEEDS BE PLANTED?
=Experiment.=--Plant several kernels of corn in moist soil in a gla.s.s tumbler or jar. Put one kernel at the bottom and against the side of the gla.s.s, place the next one a half inch or an inch higher and an inch and a half to one side of the first seed and against the gla.s.s.
Continue this till the top of the gla.s.s is reached (Fig. 2). Leave the last seed not more than one-fourth inch below the top of the soil. The soil should be moist at the start and the seeds should all be against the gla.s.s so they can be seen. This can best be done by planting as you fill the gla.s.s with soil. Plant peas and beans in the same way. Do not water the soil after planting. Set aside in a warm place and wait for the seeds to come up.
Another method of performing this experiment is to make a box having one side gla.s.s (Fig. 46). The length and the depth of the box will depend upon the size of the gla.s.s you use. Fill the box nearly full of moist soil and plant seeds of corn and beans and peas at depths of one-quarter inch, one inch, two inches, three inches, and four inches. These seeds can best be put in as the box is being filled.
Hold each individual seed against the gla.s.s with a stick so that when planted they may be seen through the gla.s.s. Protect the seeds and roots from light by using a sheet of cardboard, tin or wrapping paper or a piece of board, and set in a warm place.
Many of the seeds planted only one-quarter inch deep will not sprout because the soil about them will probably dry out before they take from it enough moisture to sprout. The one and two-inch deep seeds will probably come up all right. Of the three and four-inch deep seeds, the corn and peas will probably make their way to the surface because they send up only a slender shoot, which can easily force its way through the soil. The deep-planted beans will make a strong effort but will not succeed in forcing their way to the surface because they are not able to lift the large seed-leaves through so much soil, and will finally give up the struggle. If any of the deeper beans do get up, the seed-leaves will probably be broken off and the little plant will starve and be dwarfed. This experiment teaches us that we should plant seeds deep enough to get sufficient moisture for sprouting and yet not so deep that the young seedlings will not be able to force their way to the surface.
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.
[Ill.u.s.tration: FIG. 42.
To show how the bean plant gets up. Notice the curved hypocotyls pulling the seed-leaves or cotyledon out of the soil.]
[Ill.u.s.tration: 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.]
[Ill.u.s.tration: 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 quant.i.ties 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.
For the larger operations of the farm and market garden, hand and horse-power drills and broadcasters are generally used, though some farmers still plant large fields by hand.
The gra.s.ses and clovers are generally broadcasted by hand or machine, and are then lightly harrowed and are generally rolled.
The small grains (wheat, oats, etc.) are broadcasted by many farmers, but drilling is considered better. With the grain drill the seed is deposited at a uniform depth and at regular intervals. In broadcasting, some of the seeds are planted too deep, and some too shallow, and others are left on the surface of the soil.
From experiment it has been found that there is a loss of about one-fifth of the seed when broadcasted as compared with drilling.
As in the case of gra.s.s seed, the grains are generally rolled after sowing.