Seeds Of Tropical Africa

All plants start life as seeds. A seed is really a very young plant all ready to grow and containing a very small root and a shoot which is to grow up and become the stem and the leaves. Protecting the tiny and very delicate root and shoot is a skin; and packed inside this skin along with the root and shoot there is often a supply of food for the plant to live on until it is old and big enough to get food for itself. All this can be very well seen in the bean seed, especially if it has been soaked for several hours before you examine it. You will find in the bean that it has on the outside a thick skin, along one side of which is a scar. This scar was where the seed was fastened to the pod. If you cut along the scar with a penknife and remove the thick skin the seed will easily be made to split into two halves. These two halves are called the seed-leaves or cotyledons and in them is the store of food for the young plant. Between them, at the border where the scar was, you will be able to make out a small root pointing outwards; pointing inward: is the shoot with the tiny bud containing leaves curled up at its end.

When the seed starts to grow, the root comes through a very small hole in the skin; as it gets larger the skin bursts. The root then grows downwards into the soil and gives off branch shoots. The shoot grows upwards from between the two cotyledons; as it gets above the ground it, and the tiny leaves it bears, gradually turn from white or yellow to green. The two cotyledons containing the food supply may also be pushed above the ground, when they turn green. The cotyledons supply the young growing plant with food for a time and then gradually get thinner and more shriveled until they at length disappear. By this time the root and leaves are able to get all the food necessary for the plant, which grows on apace. Another kind of seed is the maize or Indian corn seed A grain of maize is not only the seed, as is the bean, but corresponds to the seed and pod as well It is not like a pod to look at, but it resembles a pod or that it is a vessel containing the seed. if you examine a grain of maize you will see that one end is pointed and rough; this is where it was attached to the corn-cob.

The two surfaces are hard and shiny, but in the middle of one of them a line can be made out, and this shows where the young plant is lying underneath. If you soak a grain of corn to soften then mealy part grain; if you look very closely you will just be able to make out the tiny root and the shoot, and surrounding them one flattened seed-leaf or cotyledon, not two as in the bean. This one cotyledon is not thick, because it does not contain food for the young plant; it merely acts as the first leaf of the plant until new leaves develop. In the case of the maize grain the food for the young plant I. carried in the mealy portion placed all round the young root and shoot; in this case the food is not stored in the cotyledon. All flowering plants have seeds of one or other of these types, i.e., the bean type, with two cotyledons, or the maize type, with one cotyledon; of course there are great differences in the size and shape Of seeds, but not in this one point

Thus we can divide all flowering plants into two groups: those with one cotyledon and those with two cotyledons. Thorn with one cotyledon are called monocotyledons and those with two cotyledons are called dicotyledons. Other differences go band in hand with these, for example: monocotyledons have several thread-like roots arising more or less from the same point, and long narrow leaves with veins running side by side and not in a network. In this group we have such plants as corn, grasses, sugar-cane, bamboos, palms, lilies, orchids, etc. Dicotyledons have one main root with branches arising from it; to this group belong all plants which have a network of veins in their leaves. Most forest and fruit trees belong to the dicotyledons. For seeds to be able to grow they must have water, air, food and warmth.

Keep seeds quite dry and they will never grow; if deprived of air and food they will die; seeds kept in a very cold place, or if they are exposed to very cold weather, will not grow. Light is not necessary at first, but as soon as the first leaves appear light becomes necessary for the formation of the green coloring matter or chlorophyll, and for assisting to build up the food of the plant The leaves of a plant always grow towards the light The roots always grow downwards and towards moisture and darkness.