A seed is simply an artificial embryo enclosed in a hard outer shell. The development of that seed is the primary process of fertilization in seed plants, particularly the gymnosperm plants, such as the pomegranate and the ovary. The outer protective covering of the fruit of the seed, called the papilla, is called the exocarpal. While there are many kinds of seeds, their number ranges from two to more than a thousand, with some seeds being solitary and some of them being families. Some trees and shrubs also bear fruit resembling seeds.
The seeds are enclosed within a thin coating of spore-like coat, which helps them to remain dry when they pass through the placenta and into the growing leaves. The outer coating helps these seeds to protect themselves from damage caused by winds and other weather conditions. When this coating starts to wither, the plant's reproductive system starts to deteriorate, and the seeds fall off. Seed coat is also responsible for helping plants develop into different kinds or shapes.
There are two kinds of seeds - endosperm seeds and cotyledons. Endosperm seeds are the ones that you will see on the surface of a plant and are responsible for the reproduction process. These seeds are not mixed together or sown; rather they are placed one at a time onto the desired piece of land where they will eventually start growing. The cotyledon seeds, on the other hand, are the ones that are mixed together and are dispersed in the air as seeds. These seeds do not have the endosperm within their embryo; instead, they are mixed together with other types of seeds and are scattered far and wide.
Seeds can be stored for a number of reasons. If the plants become too dry, seeds can be stored in an area where they will not germinate. This is particularly important for medicinal seeds, such as the essential oil of chamomile. Other seeds, however, cannot be stored without becoming damaged, so they are often thrown away when plants are over harvested or planted in places where they will be unsightly. Seed coating is sometimes used to protect seeds from sun damage and to make them last longer.
Most animals, birds, and insects produce seeds, and these can be transferred to people, plants, and other things by means of insects and birds. In certain cases, seeds can be infectious among living things. Ants do this regularly, for instance, but other insects, such as bees and wasps, are more likely to transfer the seeds to plants. Sometimes, ants will go so far as to put the seeds into their nests and make sure that they are continually pollinating.
Seeds are usually coated in a thin film of seed coat that prevents them from germinating fully and from making themselves known. This makes seeds hard to find, but seeds can sometimes be found partially developed, with some of the coating still attached. This makes them easier to find and seed coats mean that they will germinate sooner.
The plant that a seed germinates from does not necessarily have to be alive to give birth to seeds. Seeds can be produced from a simple living cell, called a zygote. A zygote can contain many thousands of small seeds, and the life cycle can be very easy. If a plant or animal produces seeds, it must divide and then divide again before it can reproduce. After a while, the seeds will be covered with a thin film of skin, called a cuticle, which protects the seeds from the harsh environment in which they grow and sprout.
Seed plants can be either fleshy, which means they need to be taken care of, or soft. Fleshy plants are less well known, but they too have a limited lifetime. Soft seed plants usually live for a few months and then die, so they can be stored and passed on as family heirlooms.