Page:Popular Science Monthly Volume 55.djvu/710

690 experience of florists, who always seek to obtain a white variety from which to develop the desired hue.

Red flowers are much rarer than blue, and both are seldom common in the same family. For instance, in the pink family red and white blossoms prevail, and there are no blue shades. The pinks are crimson and scarlet, often with elegant markings and a strong aromatic odor. The honey is deeply concealed, and they are visited almost exclusively by butterflies and millers. Twenty-eight species of diurnal Lepidoptera have been collected upon a single variety of Saponaria. Of the eighty species of Rosaceæ, thirteen are red and two purple, but the forty-four white flowers are very generally tinged or tipped with red. The two purplish-flowered species, Geum rivale and Potentilla palustris, belong to genera in which yellow predominates, and this primitive color is still evident in both their calyx and corolla. There are no blue or violet flowers. This family exhibits a marked tendency both in stem, leaf, bud, flower, and fruit to develop reddish coloration, a tendency which is probably due to the chemical constitution of the sap. There are no flowers in this family adapted to Lepidoptera, but they are visited by a mixed company of flies, beetles, and Hymenoptera. The smaller and less specialized Rosaceæ are yellow and white and are visited by a variety of short-lipped insects. With the increase of the flower in size and conspicuousness the number of insect visitors greatly increases, and the enlargement of the flower is attended by red coloration. Owing to the chemical constitution of the nutritive fluid, probably to its acidity (for when the petals of a rose are treated with ammonia they become blue), there has been no opportunity for the development of blue coloration by insects. With the enlargement of the perianth and the increased flow of sap, red tints have tended to appear by process of oxidation.

The correlation of red coloring with an increased flow of sap is well illustrated by the galls of the wild-rose tree, which are often "as rosy as the rosiest apple." An abnormal flow of sap is caused to the part stung by the insect, and red coloration is due to the action of light, for it is of no service to the plant. Again, when the flowers of Cratægus coccinea are stung by the gall-fly the different organs all become bright red, and the change in coloring is accompanied by an increase in size. In some instances red colors, according to Darwin, indicate greater vigor on the part of the plant, and I have also observed that the dwarfing of red flowers under cultivation may cause them to revert to white.

It was long, indeed, believed that the same species could not produce yellow, red, and blue flowers. But this doctrine, to use the words of Dr. Lindley, "must now be laid up in the limbo of pleasant