THE INDIVIDUAL FLOWER
A complete flower consists of stamens and pistils (the organs of reproduction), and calyx and corolla (the floral envelops which protect the stamens and pistils). But any one of these organs may be absent.
The calyx is the outer floral envelop, which is more often green, though it is sometimes colored. It may consist of a number of separate parts, called sepals, or these may be more or less united.
The corolla is the inner floral envelop. It is usually colored, and forms the most beautiful feature of the flower, and plays an important part in attracting insects to it, which may carry on the work of fertilization. It may consist of a number of separate parts, called petals, or these may be more or less united, in which case the corolla is said to be gamopetalous. When the calyx and corolla are much alike, and seem like one floral circle, this is referred to as a perianth.
The stamens and pistils are called the essential organs of a flower, because they are necessary to the maturing of the fruit.
Perfect flowers have both sets of essential organs.
Imperfect flowers have but one set of essential organs.
Staminate (or male) flowers have only stamens;
Pistillate (or female) flowers have only pistils.
Neutral flowers have neither.