"From what has now been stated, it appears to result that modifications of chromule are the cause of the diversity of colors; and that these modifications depend principally upon the degree of oxygenation. In leaves fully developed the chromule is green; it gains a tendency to yellow or red when it is more oxidized, as one perceives by the changes of the color of leaves in autumn, by the effect of acids; and it appears to verge to blue when it is less oxidized. We know that the flower of the Hydrangea becomes blue in a soil sufficiently impregnated with iron."
"The nature of this work does not admit of a very extensive discussion of this subject in its pages, but it may be well to show that plants do contain metallic oxides."
"Dr. Sprengel, in a German publication called Der Land und Hauswirth, or the Agricultural and Domestic Economist, states that in almost all plants analysis discovers more or less iron, and as the atmosphere does not contain any sensible quantity, it must be admitted that it is derived from the soil."
"In Sir Humphrey Davy's Agricultural Chemistry, it is stated that the only metallic oxides found in plants are those of iron and manganese, but there is little doubt that copper exists in the Rose, as may be verified by leaving a clean linen rag in rose water or in the water in which rose leaves have been steeped; after some days it will turn green, and copper may be detected, even when the rose water has been distilled in glass or new tin vessels. I remember to have seen a scientific account in some French publication, of gold being extracted from the sage plant, although in very small quantities. Iron and manganese would however be sufficient to produce almost every variety of color known."
"Immediately after the flower withers, a change in the juices of most plants takes place, by which change the font or seed is matured; this is very perceptible in the eatable fruits, and proceeds until acidity becomes obvious to the taste; after this saccharine juice is formed - now if iron in a low state of oxidation be the coloring substance of a flower, it is clear that as soon as the juice of the plant becomes more acid, a farther oxidation takes place, this would cause a change in color."
"I would instance the Lilac. Iron in a low state of oxidation combined with manganese and carbonic acid, form component parts of a mineral called Pearl-spar, which is of a brilliant white - it may therefore exist in the same state in the white Lilac; and the manganese is often found, particularly in the Tiree marble, to be the cause of lilac color - as the juices ripen and grow more acid, the iron is farther oxidized, the flowers fade, turn of a rusty brown, and finally the seed vessel ripens of a dark brown."
That Iron is able to produce almost every variety of color we may learn from the fact that the native minerals, Phosphate of iron is of all shades of blue. Sulphate and arseniate of iron, are green, brown, yellowish red, brownish green. Humboldtine or oxalate of iron is bright yellow, etc., etc.
Manganese is also found of most colors, from the greenish blue of the Horn Mangan to the rose red of the Tiree marble.
"The amethyst is supposed to be colored by iron and manganese, the emerald by oxide of chrome; the topaz, the sapphire and the ruby by iron."
"It is well known to the florist that over manured soil deepens, or spoils, as he calls it, the colors of his tulips and other favorites, and that from this deterioration it is difficult to recover them.
"Strong manure contains a large proportion of alkali, and this always deepens and rather deadens many colors, particularly of the red and purple tinge, while acids on the contrary lighten and enliven them; this consideration may be experimentally applied to the subject."
A number of years since I sold to a Tulip amateur a bed of choice varieties of this flower, which had bloomed in my own garden the previous year, which I knew to be very fine. At the time of their flowering in his garden, he came to me in a great rage, bringing with him a handful of the Tulips, and accused me of selling him a lot of inferior bulbs for the very best. They were indeed inferior, except in shape. I examined them, and found the ground color to be a dull brown, with stripes a few shades darker. I could not believe they were identical with those I sold him, but had some suspicions they might be the same, but had not received proper treatment. He invited me to visit his garden and judge for myself. The journey of 25 miles I cheerfully undertook, and found to my surprise, that not only my own Tulips, but also those obtained from two other sources, were indeed a sad sight, all pretty much in the same style and worthless. But I was not surprised when the mode of their cultivation had been detailed. He had not only prepared his beds with a large quantity of strong manure, but to cap the climax, he covered the bed in autumn with four inches of tanner's hemlock bark as a protection. The leaching of the hemlock bark, and heavy manuring, satisfactorily explained the cause of the disaster, not only to myself, but to the gentleman also, when we presented the facts before my friend, Mr. Teschemacker, who affirmed that their treatment was sufficient cause of their deterioration. The inquiry was then made, how the flowers could be brought back to their original beauty. The answer was, that it was doubtful whether that could be done, but it was suggested, that the only probable means would be, to form a compost of virgin soil from a pasture without any manure, with sand and lime rubbish. - It, however, was not successful.