Colors of Flowers.— Although the colors of flowers are very numerous and of many hues and shades, yet it is possible, usually, to segre gate the flowers into two groups, the blue and the yellow. With each of these we may find red and white. It has been estimated that in an average collection of 1,000 plants about 284 have white flowers, 226 yellow, 220 red, 141 blue, 73 violet, 36 green, 12 orange, 4 brown and 2 black. Of these those with white flowers are almost universally fragant, with agreeable odors. Red flowers are usually more fragrant than yellow ones. The colors are due to pig ments either dissolved in the cell sap or held in the chromoplastids. The latter is the case with many of the reds, oranges and yellows, which are due to carotin or some of its deriva tives. The blues, violets and purples are due to a variety of substances in solution, known col lectively as anthocyanin. In reality this is not a single substance but a group of chemically related compounds. Other groups of pigments are also present in some flowers. The whole subject is a very difficult one as on account of the non-crystalline nature of some of these coloring matters they cannot be obtained in a pure state and so are not easily investigated chemically. .
Flowers of the The features that make flowers attractive or useful to man are chiefly the bright colors, form and odor. These may be combined, all in the same flower, as in the Easter lily whose beautiful white color is matched by its graceful form and delightful odor; or the flower itself may be inconspicuous and have only its odor to make it welcome, as in the Mignonette. Other flowers may attract by their color and shape and entirely lack scent or even be disagreeable in odor. There is a fashion in flowers as in dress, so that many flowers popular a generation ago are not found now except in old-fashioned gardens.
In a large number of cases the flowers culti vated have undergone °doubling,* i.e., instead of
the single whorl of petals there are many petals. The extra ones represent perhaps most often stamens that have been transformed to petals under the influence of conditions that are not well understood. In heads of flowers such as those of the sunflower where usually only the external circle of flowers is showy and the remainder rather inconspicuous, the doubling consists of the transformation of these central inconspicuous flowers into showy ones like those at the margin. This is also the case in the cultivated snowball bush in which all the flowers are sterile and showy instead of merely the marginal ones of the cluster as in the wild form.
Many of the most beautiful of the cultivated flowers are not found in nature but are the re sult of the plant breeder's art. See PLANT BREEDING.
Some of the commoner flowers have been in cultivation from antiquity, as in the case of the rose and pink, and have been discussed even in the writings of the ancients. On the other hand it has been only within the past hundred years or so that the systematic exploration of the world has revealed myriads of new plants many of which have been brought directly into cultivation or been made the subjects of the breeder's skill in improving sorts already known. It should be noted, for example, that in America the Canna was rarely grown until at the World's Fair at Chicago in 1893 the exhibit of new and gorgeous sorts in massed groups showed the value of this plant. The common blue Iris has been found in gardens for centuries but until recent years it has been only in large estates and botanical gardens that the showy sorts, white, cream, yellow, red and varicolored were to be found, while now they are accessible to every flower lover. See BOTANY; FLOWERS AND INSECTS; FRUIT; GARDEN; INFLORESCENCE;