LUMINOUS FLOWERS.
Among the earliest observers of phosphorescent flowers may be mentioned
a young Swedish girl, the daughter of Linnæus, the eminent naturalist.
While walking in the garden one sultry night, she saw what was
described as a “lightning-like phosphorescence” about the flowers of
the nasturtium (_Tropæolum majus_). The sparks, or flashes, were also
visible early in the morning, but, curiously enough, were not apparent
in complete darkness; the time between day and night evidently being
the most favorable for the exhibition. This observation was made in
1762, and the young girl lived to the advanced age of ninety-six, often
repeating the story.
In 1843 Mr. Dowden, an English botanist, noted a similar display in
the double variety of a common marigold. Several friends were with
him at the time; and, by shading the flower, they distinctly saw a
golden-colored lambent light playing from petal to petal, so that an
almost uninterrupted corona was formed about the disk.
Others have observed this peculiarity in this flower and in the hairy
red poppy (_Papaver pilosum_). A correspondent of the “Gardner’s
Chronicle” writes, “We witnessed (June 10, 1858) this evening, a little
before nine o’clock, a very curious phenomenon. There are three
scarlet verbenas, each about nine inches high, and about a foot apart,
planted in front of the greenhouse. As I was standing a few yards from
them, my attention was arrested by faint flashes of light passing
backwards and forwards from one plant to the other. I immediately
called the gardener and several members of my family, who all witnessed
the extraordinary sight, which lasted for about a quarter of an hour,
gradually becoming fainter, till at last it ceased altogether. There
was a smoky appearance after each flash, which we all particularly
remarked. The ground under the plants was very dry; the air was
sultry, and seemed charged with electricity. The flashes had the exact
appearance of summer lightning in miniature. This was the first time
I had ever seen any thing of the kind; and having never heard of such
appearances, I could hardly believe my eyes. Afterwards, however,
when the day had been hot and the ground was dry, the same phenomenon
was constantly observed at about sunset, and equally on the scarlet
geraniums and verbenas. In 1859 it was again seen. On Sunday evening,
June 10, of that year, my children came running in to say that the
lightning was again playing on the flowers. We all saw it; and again on
July 11, I thought that the flashes of light were brighter than I had
ever seen them before.”
It has been asserted that this phenomenon was due to optical illusion,
but the experience of Goethe points to a different conclusion. He says,
“On the 19th of June, 1799, late in the evening, when the twilight
was passing into a clear night, as I was walking up and down with a
friend in the garden, we remarked very plainly about the flowers of
the Oriental poppy, which were distinguishable above every thing else
by their brilliant red, something like flame. We placed ourselves
before the plant, and looked steadfastly at it, but could not see
the flash again, till we chanced in passing and repassing to look at
it obliquely; and we could then repeat the phenomenon at pleasure.
It appeared to be an optical illusion, and that the apparent flash
of light was merely the spectral representation of the blossoms of a
blue-green.”
It is an interesting fact, that the light has been observed principally
about yellow flowers, as the sunflower (_Helianthus annuus_), the _Rose
d’Inde_ and _Oeillet d’Inde_, the garden marigolds (_Calendula_),
yellow lily, and others.
The Swedish naturalist, Professor Haggern, was fortunate in observing
the light about the marigold. His first impression was, that it was
an illusion; and to convince himself, he placed a man near at hand
with orders to make a signal when he saw the light: the result was,
that both observed it simultaneously. The light appeared as a flash,
often in quick succession from the same flower, and again only after
several moments. It was only observed at sunset on dry days. Professor
Haggern’s observations were made upon the marigold, garden nasturtium
(_Tropæolum majus_), the orange lily (_Lilium bulbiferum_), and the
French and African marigolds (_Tagetes patula_ and _T. erecta_). He was
at first disposed to consider the light due to some insect, but finally
decided that it was electrical.
In 1857 the press of Upsala, Sweden, contained accounts of remarkable
lights that had been observed about a group of poppies in the Botanic
Gardens. The observer, M. Th. Fries, a well-known botanist, in passing
the flowers, noticed three or four emitting little flashes of light.
Believing that he was the victim of an optical illusion, and wishing
to satisfy himself, he took a friend to the place at the same hour on
the following night, without, however, informing him what he had seen.
The latter immediately noticed the light, and soon the garden was
thronged with persons interested, who wished to see the flowers that
“threw out flames.” Later, fourteen persons saw the exhibition at once,
not only upon the _Papaver orientale_, but on the _Lilium bulbiferum_;
and before the curious phenomenon ceased, over one hundred and fifty
reliable observers were enabled to testify to the delight they had
experienced in watching the gleams of light play about these flowers;
the doubters and critics, of which there were many, being effectually
silenced.
[Illustration:
PLATE XXI.
LUMINOUS UMBELLULARIA.
LUMINOUS FISH.
(_Chauliodus._)
SILICIOUS SPONGE.
LUMINOUS CORALS.
LUMINOUS CRUSTACEAN.
(_Ptichogaster._)]
It is usually the misfortune of the single observer, or the minority,
to be ridiculed, and their word doubted, simply because others do not
choose to believe their statements. That such a course is unjust, is
well shown in the instance of the daughter of Linnæus, who made the
statement, that as she approached the flowers of _Dictamnus albus_ with
a light they appeared to ignite, without, however, injury to them. This
experiment was tried time and again by others, but without success;
and not a few scientists of the day regarded it as a delusion, while
others averred that it was pure invention; opinions which placed the
lady in a disagreeable position. Some years after, Dr. Hahn was enabled
to show that the experiment was not mere fiction. He says, “Being in
the habit of visiting a garden in which strong, healthy plants of
_Dictamnus albus_ were cultivated, I often repeated the experiment, but
always without success; and I already began to doubt the correctness
of the observation made by the daughter of Linnæus, when, during the
dry and hot summer of 1857, I repeated the experiment once more.
Fancying that the warm weather might possibly have exercised a more
than ordinary effect upon the plant, I held a lighted match close to an
open flower, but again without result; in bringing, however, the match
close to some other blossoms, it approached a nearly faded one, and
suddenly was seen a reddish, crackling, strongly shooting flame, which
left a powerful aromatic smell, and did not injure the peduncle. Since
then I have repeated the experiment during several seasons; and even
during wet, cold summers it has always succeeded, thus clearly proving
that it is not influenced by the state of the weather. In doing so, I
observed the following results, which fully explain the phenomenon.
On the pedicels and peduncles are a number of minute reddish-brown
glands, secreting etheric oil. These glands are but little developed
when the flowers begin to open, and they are fully grown shortly after
the blossoms begin to fade, shrivelling up when the fruit begins to
form. For this reason the experiment can succeed only at that limited
period when the flowers are fading. The radius is uninjured, being too
green to take fire, and because the flame runs along almost as quick as
lightning, becoming extinguished at the top, and diffusing a powerful
incense-like smell.”
As to the actual cause of these exhibitions of light, little is known.
In the case of M. Fries, the luminosity was always observed between
quarter past ten and quarter past eleven in the evening, and especially
when the weather was sultry, and was seen to best advantage when the
observers were not looking at the flowers directly. The light appeared
in fitful flashes, similar to that seen about the other flowers
mentioned, and was supposed to be electric. Mr. Haggern was also
inclined to believe that the phenomenon observed by him was electric.
The flame seen about the flower ignited, by the daughter of Linnæus,
was caused, as suggested by Phipson, by the ignition of the inflammable
atmosphere that envelopes the essential oil-glands of certain
_Flaxinellæ_. Electric light has been observed in a plant allied to the
palm, belonging to the genus _Pandanus_. When the spatha, or covering
which envelopes the flowers, is ruptured, a crackling sound is heard,
and a spark of light emitted. It is not impossible that the light of
certain flowers is in some way attendant upon the escape of pollen.