In the lily it should be further noticed that the sepals and petals are all separate, but in many flowers they are united in various ways to form urns, tubes, funnels, trumpets, etc. The common morning glory is an illustration of a flower in which the petals are united so as to form a beautiful trumpet-shaped or funnel-form corolla.
The general purpose of the perianth, that is, the two outer parts of the flower, is to protect the far more important inner parts in the bud, and when the flower opens the perianth unfolds and exposes the inner parts, which are then ready for their peculiar work.
The bright color usually shown by the corolla, and sometimes also by the calyx, as in the lily, is probably associated with the visits of insects, which come to the flower for nectar or other food. Since it has been found, however, that some visiting insects are color blind, it is doubtful whether the color is so universal an attraction as it was once thought to be, but it is certainly associated with some sort of important work.
A summary of these various duties is as follows: The green, leaf-like calyx is certainly for bud protection; the brightly colored corolla (and sometimes calyx) adds to the duty of protection that of attracting necessary insects, or some other duty that we do not as yet understand.
Just within the corolla the third part or set appears, consisting of six stamens. These six stamens are also in two sets of three each, an outer and an inner one. Each stamen consists of a long stalk-like part, called the filament, and at the summit of the filament is borne the anther, which in the lily consists of two long, narrow pouches lying side by side. When the anther is ripe these pouches are filled with a yellow, powdery dust called the pollen. Each particle of this dust-like pollen consists of a minute, but beautifully organized globular body, known as the pollen-grain. The anther pouches are therefore full of pollen-grains.
RED OR WOOD LILY.
(Lilium Philadelphicum)
In the lily it will be noticed that when the anthers are ripe and the pollen is ready to be shed, a slit opens lengthwise in each of the two pouches or sacs. This is the common method for opening the anther sacs, but in some flowers it is curiously modified. For example, in the heaths, such as the huckleberry, the sacs open by a hole at one end, and sometimes the tips of the sacs are drawn out into long, hollow tubes through which the pollen is discharged. In other cases, as in the sassafras, the sacs open by little trap doors, which swing open as if upon hinges.
Of the two parts of the stamen, the filament and anther, the latter is the essential one, so that in some cases the filament may be lacking entirely, only the anther appearing to represent the stamen. Furthermore, the essential thing about the anther is the pollen, to manufacture which is the sole purpose of the stamen.