WM. Brockbank: The Artificial Coloration of Flowers.

Scientific American 24, 11.12.1897

By WM. Brockbank.

The excitement about blue carnations led my neighbor, W. Darrington, and myself to endeavor stave the mystery by imitating it, and we soon discovered that, although flowers could not be tinted by immersing them in dye solutions, they could readily he colored by placing their stalks in aniline solutions.

Aniline scarled dissolved in water to about the transparency of claret has very rapid action on flowers, coloring them pink and scarlet. Indigo carmine produce, beautiful blue tints. The two combined dye various shades of purple, with curious mottled effects, some parts of the flowers becoming pink and other parts blue and purple. Greens are produced by using the blue dye with yellow. We also tried indigo and cochineal, with partial success. Lily of the valley flowers became beautifully tinged with pink or blue in six hours; narcissi are changed from pure white to deep scarlet in twelve hours, and delicate shades of pink are imparted to them in a very short time. Yellow daffodils are beautifully striped with dark scarlet in twelve hours; the edges of the corona also become deeply-tinged, and the veining of the perianth becomes very strongly marked. Cœlogyne cristata, lapageria albs, calla æthiopica, cyclamens, snowdrops, leucojums, hyacinths, Christmas roses, Solomon's seal, tulips, and many other flowers were succesfully treated, and many leaves were found to become colored very quickly by the process. I send you herewith a number of examples.

The more interesting question of how this rapid change in brought about soon attracted my attention, and caravel extremely interesting. The coloration is mainly confined to the vessels.

There is a system of veins its plates, the vein tubes being clearly seen under the microscope passing throgh the leaves, petals and other parts of the flower. In these tubes the motion of the colored water can be seen, and it became evident thatt it was by these that the color is conveyed and left in every portion of the plants. In the case of cut flowers, the action is very rapid, the water tubes beginning at once to absorb the fluid, which was passed along by either capillary attraction, contraction, or possibly by some more active life-force acting with-in the veins. My experiments in proof of this were made of first entirely with cut flowers. I afterward tried the experiment by taking a Roman hyacinth very carefully out of the soil, and placing the roots its aniline water. In twelve hours the petals began to color, and the flowers gradually became pink tinted throughout. This experiment was repeated on many narcissi and other bulbs. It cannot, however, be said that the root fibers were unbroken; probably they were so, as I have failed to color any flower by merely watering the soil with colored water. The filtering appendages to the roots evidently prevent the absorption of much of the color, as the petals of the flowers do not become either so quickly or so deeply tinted when the plant has its root as with cut flowers. It was, however, clearly seen that the vein tubes proceeded from the roots, thus completing the water system of tubes from root to flower.

The veins when colored are beautifully seen under the microscope as clear tubes running in parallel lines, the interspaces filled by cellular matter. The tubes gradually branch out as they proceed, and as they approach the margins they are often finely branched. When the colored water renews the margins of the petals they thus become deeply tinctured, especially in the narcissi, illustrating the cause whereby the daddofil so frequently obtains the deeper color at the edge of the corona. It is the same with the leucojum and the snowdrop.

Very singular results were obtained in the variegated leaves of the aucuba and ivy—plants which to the winter season, one would suppose, had the leaves quite dormant. Single leaves with their stalks placed in aniline dye water, began to color in about three hours, and in twelve hours had their margins deeply colored. They were thus shown to have the absorptive power, quite apart from the stem.

Another remarkable instance was seen in lapageria alba, which has a very thin wiry stalk and a large waxy flower. With the stalk placed in dye water, the whole flower became beautifully veined with pink in three or four hours — a singular fact, when one considers the minuteness of the tubes through which the liquid has to be drawn. It is difficult to believe that this can be accomplished by capillary attraction only. In eucharis amazonica, which has thick stalks, the flower does not become tinted at all, but the style is dyed a deep red. The pistils of flowers always become deeply colored, which is an important fact, showing that the solid matter of the coloring solution is thus secreted [deposited in] by the fruiting vessels of the flower.

White tulips furnish excellent illustrations of artificial coloring, as they can be readily tinted either pink, blue, green, or purple in a few hours. The vein tuben which are thus displayed in the petals agree with the strongly marked features, known as the "flamed" or "feathered" varieties of the florist. It is generally known that all tulips raised from seed are self-colored when they first bloom; they are then called "breeder tulips," and the enthusiastic amateur florist grows on his "breeders" for six or seven years until they "break," when they become either "flamed" or "feathered" varieties. Now a florist may ascertain its six hours whether his breeder tulip will become a feathered or flamed sort, and whether it will be worth growing on for the breaking time, because the veining of the petal is shown by the color, and it is that which makes the feature when the tulip is fully matured. Blue tulips hare always been desired, and they can thus be artificially produced for florist purposes.

Daffodils end narcissi generally can be greatly varied in color, and especially by showing their exquisite veining when thus treated. The tube and corona take s darker and richer tone of color than the perianth, thus agreeing with the fact that all daffodils are more or less bicolor. The Christmas rose is also an interesting flower when artificially colored. Straight tubes cross the petals from base to point, with numerous cross tubes, and the main ones branch out augularly, thus dividing the snow-white petals into a network of red lines. The interspaces are filled with oval cellules, and as the tubes are permeable, the cellular spaces become suffused with a delicate shade of pink. Snowdrops and leucojums are also very interesting when thus treated. Their petals are veined with about eight tubes at the base, which pass across the petal to its point in nearly parallel lines, strongly and clearly marked. These are branched near the tip of the petal in fan-like form, producing rich pink margins to the flower. The double white camellia is another very pretty illustration, as it easily assumes a pink shade throughout. It is difficult to imagine how this is done, as the camellia has a small woody stalk; and in the case of a double flower, with forty or fifty petals, the attachment of each of them to the tubes in the stalk must be very slight, and yet every petal becomes tinted in a few hours.

White lilac takes the color perfectly, becoming either pink or blue at pleasure. The abutilon has the calyx colored, but not the petals. These are already strongly vein-marked, and they seem to refuse the new comer. Primulas take the color readily, but the common wild primrose will not be changed. Forced leaves of the Swede turnip, grown in the dark for culinary purposes, are extremely susceptible to coloration. They begin to color in about three hours, and in twelve hours are beautifully fringed with red, and suffused with rich orange. Thus tinted, they are beautiful objects for table decoration.

- Gardeners' Chronicle.