THE COLORATION OF FLOWERS

From ‘The Colors of Flowers’

The different hues assumed by petals are all thus, as it were, laid up beforehand in the tissues of the plant, ready to be brought out at a moment’s notice.  And all flowers, as we know, easily sport a little in color.  But the question is, Do their changes tend to follow any regular and definite order?  Is there any reason to believe that the modification runs from any one color toward any other?  Apparently there is.  The general conclusion to be set forth in this work is the statement of such a tendency.  All flowers, it would seem, were in their earliest form yellow; then some of them became white; after that, a few of them grew to be red or purple; and finally, a comparatively small number acquired various shades of lilac, mauve, violet, or blue.  So that if this principle be true, such a flower as the harebell will represent one of the most highly developed lines of descent; and its ancestors will have passed successively through all the intermediate stages.  Let us see what grounds can be given for such a belief.

Some hints of a progressive law in the direction of a color-change from yellow to blue are sometimes afforded to us even by the successive stages of a single flower.  For example, one of our common little English forget-me-nots, Myosotis versicolor, is pale yellow when it first opens; but as it grows older, it becomes faintly pinkish, and ends by being blue, like the others of its race.  Now, this sort of color-change is by no means uncommon; and in almost all known cases it is always in the same direction, from yellow or white, through pink, orange, or red, to purple or blue.  For example, one of the wall-flowers, Cheiranthus chamoeleo, has at first a whitish flower, then a citron-yellow, and finally emerges into red or violet.  The petals of Stytidium fructicosum are pale yellow to begin with, and afterward become light rose-colored.  An evening primrose, Oenothera tetraptera, has white flowers in its first stage, and red ones at a later period of development. Cobea scandens goes from white to violet; Hibiscus mutabilis from white through flesh-colored to red.  The common Virginia stock of our gardens (Malcolmia) often opens of a pale yellowish green, then becomes faintly pink; afterward deepens into bright red; and fades away at the last into mauve or blue.  Fritz Mueller’s Lantana is yellow on its first day, orange on its second, and purple on the third.  The whole family of Boraginaceae begin by being pink and end with being blue.  The garden convolvulus opens a blushing white and passes into full purple.  In all these and many other cases the general direction of the changes is the same.  They are usually set down as due to varying degrees of oxidation in the pigmentary matter.  If this be so, there is a good reason why bees should be specially fond of blue,