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.

[Illustration:  FIG. 39.  A seed-tester, consisting of two plates and a moist cloth.]

[Illustration:  FIG. 40.—­A SEED-TESTER.  A plaster cast with cavities in the surface for small seeds.]

[Illustration:  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 glass tumbler or jar.  Put one kernel at the bottom and against the side of the glass, 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 glass.  Continue this till the top of the glass 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 glass so they can be seen.  This can best be done by planting as you fill the glass 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.