Flowers are always regular in their rudimental state—whorls of elevated points or some of these, however, are not infrequently abortive, whilst more frequently, some acquire a greater development than others of the same whorl, making the whorl and the flower irregular; and greater varieties of form are common in the metamorphosed leaves which compose the flower than in true leaves themselves. The internodes, or portions of the axis between the whorls, are sometimes also peculiarly developed into disk (q.v .),gynophore, etc. The different whorls often differ in their wstication (q.v.). But a beautiful symmetry may generally be traced in the arrangement of the parts of flowers, the whorls consisting of the same number of parts, and the parts of each whorl being placed opposite to the spaces of time whorl exterior to it; and this symmetrical plan of the flower remains manifest even when them is abortion or extraordinary devel opment of particular parts. The number of parts in the pistil is, however, often smaller than in the'exterior whorls; and sometimes particular parts appear to be divided, and so apparently multiplied, as the long stamens of the cruciferce, each pair of which is to be regarded as one stamen split into two, and has its place accordingly among the parts of the flower.
The development of flowers in most cases follows the complete formation of the stem-leaves, more rarely precedes or accompanies it. The unfolding of the parts of a Mower is called its flowering or blossoming, and when their functions are performed, it fades; the floral envelopes, the stamens, and even the styles, sometimes falling off early, and some of them sometimes remaining in a withered state until the ripening of the fruit; the calyx not unfrequently undergoing such modifications as to convert it into a part of the fruit itself.
In the greater number of plants, flowering takes place, during the flowering season, indiscriminately, at all hours of the day; and the.flowers once opened, remain open, even during night, till they fade. In many plants, however, a sleep of flowers takes place; they open and close with the returns of day and night. Thus, sunflowers open in the morning, and close at evening; whilst there are other flowers which open in the evening, and close in the morning. Others also open and close at certain hours of the day; thus the flowers of the common purslane open about 11 o'clock A.M. , and close soon after midday; anthericum pomeridianum opens its flowers about 2 P.m., and closes them before night; the large fragrant blossoms of areas grancliflorus open between 7 and 8 P.m., and its sleep commences soon after midnight. In a few plants, the sleep ing and waking of the flowers are regulated by the conditions of the weather. The waking and sleeping of flowers either continues for several days in succession, as in some species of meZm,bryanthemum; or the brief life of the flower ends when it first sleeps, as in the tiger-flower.
The odors of flowers, extremely various, often delightful, and sometimes very offen sive, are in some cases equally powerful as long as the flower is open; in others, they vary in strength at different times of the day. Some flowers, as those of hesperis tristss and pelargonium triste, although remaining open during the day, diffuse their fragrance only when night comes on. The oriental hyacinth, so commonly cultivated in win
dows, is at all times perceptibly fragrant, but fills the atmosphere of the apartment with its perfume about 11 o'clock at night.
The colors of the different parts of- flowers, the variety and beauty of which render many of them so attractive, generally remain unchanged, but sometimes undergo changes during the life of the flower. The flowers of myosotis versicolor —a small species of forget-me-not, very common as a weed in gardens—are sulphur-yellow when they first open, and afterwards change to blue. The petals• of cheirccnthus mutabilis, when they first expand, are and afterwards pass to orange, red, and finally purple. In hydrangea hortensis, familiar as a window-plant, the 'flowers are at first green, then rose-color, purplish red intermixed with green, and finally, when about to fade, they are of a sickly green. Some flowers undergo remarkable changes of color during the day, as those of the. common pink phlox, which, early in the morning, are light blue, and become bright pink as the day advances; and those of hibiscus variabilis, which are white in the morning, pink at noon, and bright red at sunset.
The colors and odors of flowers are subjects in the investigation of which physiolo gists have not yet been able to go far. The chemical products on which they imme diately depend are partially known; but how the chemical changes are wrought, and what various purposes they all serve as to the plant itself, can scarcely be said to have even begun to be ascertained. Both colors and odors are more or less owing to the action of the sun's rays. They are also sometimes modified by soil; and diversities of color have been obtained in cultivated flowers by changing the soil in which they grow.
A few flowers are edible, although none are of any importance on this account. Some, or parts of them, are used in dying; but notwithstanding the beauty and variety of the colors of flowers, a very small proportion of vegetable dye-stuffs is obtained from them; and a similar remark is applicable to their medicinal use. For dyeing and painting, the colors of flowers can seldom be obtained in considerable quantity, except at too great expense, and seldom of brilliancy at all corresponding with that which they exhibit in the flower itself. They are also in general fixed with great difficulty, some yellow colors being the only notable exceptions.
Flowers being subservient to the reproduction of the species, are, in all not unfavor able circumstances, followed by fruit (q.v). This, of course, in moncecious and dim cious plants, is the case only with the female flowers, the male flowers soon withering away when they have dispersed their pollen. See FECUNDATION and STAMEN. But even after the fecundation of the germen, and when, in the language of gardeners, the fruit is set, unfavorable circumstances—such as excessive heat or cold, drought or moist ure, want of due nutriment to the plant, or through excessive number of fruits set at once—to the individual fruit itself, often cause it to fall off early, long before it has attained its full size. See FRUIT.