This section is from the book "The Gardener's Monthly And Horticulturist V22", by Thomas Meehan. See also: Four-Season Harvest: Organic Vegetables from Your Home Garden All Year Long.
The London Gardener's Magazine gives the following translation of a paper read recently before the Central Agricultural Society of France which will be read with great interest in our country where General Pleasanton's original experiments attracted so much attention:
A series of experiments, not originally intended to prove the action of colored light on vegetation, has nevertheless brought to my notice some facts which may be of great use in horticulture.
The effects of the colored rays of the solar spectrum have already been made the subject of investigation by some of the most distinguished savants of the age. The mere enumeration of their labors would be too lengthy for repetition here.
That eminent physiologist, M. Paul Bert, has of late again devoted himself to the study of this interesting and delicate problem. But, so far, none of these researches, important as they are in their bearings on plant life, have led to any practical method of accelerating the growth of plants in an exceptional manner. Wherever colored light has been used alone, without the interposition of white light, there the plants have withered and died. M. P. Bert's experiments have furnished conclusive proof of this fact. All colors taken singly, are noxious to plants, he tells us.
It is an essential condition of vegetation that plants should not exist continually in artificially colored light. Therefore, when the conditions under which plants were intended to exist have been departed from too widely, negative results have invariably followed. But will it be the same when a plant is exposed to the action of particular rays of colored light modified by the presence of white light? Here, as I have just remarked, some facts of great importance to horticulture have come under our notice. The sensation will not have been forgotten which was created in the scientific world when M. Poey communicated to the French Academy of Sciences the marvellous results obtained by the American General Pleasanton, with vines grown in a vinery illumined with violet and white glass, and which in a very short time produced an exceptionally abundant crop of grapes.
Results as exceptional, according to the same authority, were obtained in fattening cattle and pigs by the same means. But here we have to do with plants, not with live stock. I cannot confirm these statements, but I shall no longer attempt to invalidate them, inasmuch as experiments of my own in pursuing a totally distinct line of research have taught me, as will presently be seen, that the views of the American General are not to be entirely rejected.
I shall not attempt to explain the phenomena scientifically; whether they are chemical, physiological, or merely mechanical, it is impossible for me to say. However this may be, the facts reported by M. Poey suggested to me the idea of the experiments of which I am about to speak; and if I did not exactly get what I sought, the results obtained, in my opinion, largely compensated me for my failure.
Some years back the Natural History Museum received from Monte Video a very small herbaceous plant, forwarded by a French naturalist, M. Lasseau, and labeled " Pretty little Monothacea from neighborhood of Monte Video." This humble-looking little acaules-cent herbaceous plant, consisting merely of seven or eight myrtiform leaves, justified its appelation, a pretty little plant. It grew well at the museum, but never blossomed; the blossom invariably failed, but not all at once. After the invariable fall of an almost microscopic corolla, the ovary continued its normal evolution until it at length attained full maturity. The seeds, four in number, also ripened very well. Of course it was at once seen that this was an instance of what botauists call clandestine fertilization.
M. Houlet, the able chief of the hothouse department of the museum, begged me one day to determine this curious plant for him. " Wait until it blossoms," I said. But as the blossom was very long in making its appearance, I examined the minute corolla with the microscope, and this, together with the indications furnished by the seeds, enabled me to refer it to the genus Stenandrium. The clandestine fertilization continued. A hundred times the biological conditions of this curious plant were changed without altering its temperament.
Linnaeus, in his Hortus Upsaliensis, gives a not altogether correct explanation of this phenomenon. Dillenius speaks of it under the head of buellia, in his Hortis Etkamensis, without giving a more correct explanation of the persistent anomaly.
The entire family of Acanthacese furnishes a great number of examples, with the difference that here clandestine alternates with normal fertilization. I then conceived the idea of subjecting this remarkable plant to the influence of variously colored light, by a modification of the American method. I was in hopes that the stimulus given by some one or other of the colored rays of the spectrum would enable me to determine this singular anomaly.
I mentioned my plan to the eminent professor of horticulture, M. Decaisne, who, with his usual courtesy, lost no time in placing at my disposal the necessary space, and the requisites for a series of experiments in the shape of cylindrical open-mouthed glasses, in which the light and air could circulate freely. These glasses had double sides of colorless glass. In the annular spaces between the inner and outer sides were placed colored fluids, representing six colors of the solar [spectrum. The glasses were ten to twelve inches deep, with an inner diameter of four to six inches. The annular space filled by the colored fluid in each was six to eight inches in width. In the innermost glass we stood the little plant in its little pot. The light from the sides had therefore to traverse six to eight inches of colored fluid before reaching the plant, whilst above, the white light and air entered and circulated round the plant unchecked.
"We had sown a certain number of seeds of the plant in question, and of the young plants-so raised we chose six of equal size and age, one for each glass. The fluid surrounding the first glass was a fine aniline purple or violet. That in the second glass was an ammonical solution of salts of copper, giving a beautiful blue. The third had a solution of salts of nickel, giving an equally brilliant green. The fourth was a solution of chromate of potassium, giving, a yellow color. The fifth was a solution of bichromate of potassium, producing an orange. And the sixth was a very fine aniline red.
(To be continued).