In the life of any plant, no matter how simple it may be, no matter how complex, all activities are directed towards the best possible conditions for the individual during its own lifetime and for ensuring, as far as possible, the well-being of the generation that succeeds it.
In the Flowering Plant the vegetative parts, that is, the, , and , are particularly concerned with the former aim. The latter depends, in great measure, upon the flower.
When it is realised that ais that part of the plant that bears and, conversely, a is that part of a plant that grows on a stem, then it is fairly obvious that a flower is nothing more than a specialised part of the plant, made up of different kinds of leaves, which grow on an extremely short stem.
In a typical flower there are four different kinds of leaves. These are the sepals, petals, stamens, and carpels. The production of seeds, on which the continuation of the particular species depends, is the work of stamens and carpels, and they, therefore, are the essential leaves of the flower. They are protected by the sepals and petals, which generally also take some part in regulating or directing the visits of insects.
The formation ofis followed by their dispersal. The more efficiently they are scattered, the greater is the chance of healthy lives for the plants that grow from them. As in our own human society, overcrowding is bad.
Thus the individual plant is given a fair start, more especially as there is always some provision of food as a preliminary equipment for its entry into life. When this supply is exhausted it must fend for itself. As a matter of fact, there is always enough and to spare, and the young plant is growing independently before the supply has given out.
The independence of the individual is gained by the coordination of, , and leaves in obtaining raw materials for the manufacture of food ; in providing an efficient transport system to carry this, in soluble form, to parts where it is either actively needed or where it is to be stored ; in maintaining airways, so that there is adequate circulation of oxygen throughout the whole plant-body ; in getting rid of waste material and, finally, in reacting in such a manner to the outside world that, in the struggle for existence, in the fight against long odds, ultimate individual success is achieved.