- “Proceedings of the British Association for 1843.”
- "Gardener's Chronicle," 1843, p. 691.
The tuberose has also the reputation of being luminous in a similar manner. It has been observed, so it is said, of a sultry evening, after thunder, to dart small sparks in abundance from such of its flowers as were fading. The sunflower has also a like reputation, and so has the martagon lily and the evening primrose. Altogether a number of different plants have been seen to present a similar phenomenon, and the facts are attested by a long list of different individuals.
Two theories have been propounded with respect to this class of luminosity; one that it is an optical illusion, the other that the light is electric. For the former it is contended that bright flowers are always the subjects, and this exhibition takes place in the evening. On behalf of this view, it is quoted from Goethe: "On the 19th 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 everything 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." On behalf of the electrical view it is urged that the occurrences have been observed at times when the air has been dry and charged with electricity.
A second class of luminous appearances are of the type of an experience also of the daughter of Linnæus with the dittany. When the daughter of Linnæus one evening approached the flowers of Dictamnus albus with a light, a little flame was kindled without in any way injuring them. The experiment was afterwards frequently repeated, but it never succeeded; and whilst some scientific men regarded the whole as a faulty observation, or simply a delusion, others endeavoured to explain it on various hypotheses. One of them especially which tried to account for the phenomenon by assuming that the plant developed hydrogen found much favour. At present, when this hypothesis has become untenable, the inflammability of the plant is mentioned more as a curiosum, and accounted for by the presence of etheric oil in the flowers. 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.
- “Gardener’s Chronicle,” July 16, 1859, p. 604.
- "Science Gossip," 1871, p. 122.
Possibly some of the "burning bushes" of oriental story might have a similar explanation. Vague ideas of the existence of luminous plants in India and the neighbouring countries still float about as in the days of the old Hindoos and Greeks. One of these is that in Afghanistan, to the north of Nalwo, is a mountain called Sufed Koh, in which the natives believe gold and silver to exist, and in which, they say, in the spring is a bush which at night, from a distance, appears on fire, but on approaching it the delusion vanishes. In 1845 the natives of Simla were filled with a rumour that the mountains near Syree were illuminated nightly by some magical herb. It has been suggested that this might be a species of Dictamnus, which abounds near Gungotree and Jumnotree.
A third class of examples of luminosity consists of those mythic and uncertain legends of roots which can only be recorded and not explained, possibly in many cases due only to decomposition. Josephus says "There is a certain place called Baaras, which produces a root of the same name with itself; its colour is like to that of flame, and towards evening it sends out a certain ray like lightning; it is not easily taken by such as would do it, but recedes from their hands." The only virtue this root possesses is its supposed power in the expulsion of demons.
The root-stock of a plant from the Ooraghum jungles is said to possess the peculiar property of regaining its phosphorescent appearance when a dried fragment of it was submitted to moisture, "gleaming in the dark with all the vividness of the glow-worm, or the electric scolopendra, after having been moistened with a wet cloth applied to its surface for an hour or two, and did not seem to lose the property by use, becoming lustreless when dry, and lighting up again whenever moistened."
This, or a similar plant has long been known to the Brahmins under the name of Jyotismati, and said to be produced by a species of Cardiospermum. Sanscrit authorities say that it is found in the Himalayas; and Major Madden found upon enquiry at Almora that there was a luminous plant well known there as Jyotismati or Jwalla-mat, which names imply the possession of light or fire. The Almora plant proved to be the roots of the fragrant khus-khus grass, of which only one in a hundred is said to be luminous at night in the rainy season. The roots of other grasses are reputed to possess the same properties.
If we except the milky juice or sap of two or three species, such as Euphorbia phosphorea, said to be luminous, this catalogue will exhaust the principal recorded cases of luminosity in flowering plants; our last class, which consists of luminous fungi, furnishes numerous well authenticated instances, which might be placed in two classes, of which one would include mycelium, or the root-like filaments of fungi in an imperfect state, and the other perfect or complete fungi. Schoolboys nearly half a century ago had a strong belief in "touchwood" and perhaps the belief still lingers. This "touchwood" consisted of very rotten wood, usually from the heart of a tree, deeply penetrated with the mycelium of fungi, and luminous in the dark. We remember many a cherished morsel which was carried in the pocket, for nocturnal exhibition in the dormitory, until "the light of other days had faded," which followed after a few days. One of the most extraordinary manifestations of this class of fungi is recorded by the Rev. M. J. Berkeley. "A quantity of wood had been purchased in a neighbouring parish, which was dragged up a very steep hill to its destination. Amongst them was a log of larch, or spruce, it is not quite certain which, 24 feet long and a foot in diameter. Some young friends happened to pass up the hill at night, and were surprised to find the road scattered with luminous patches, which, when more closely examined, proved to be portions of bark, or little fragments of wood. Following the track they came to a blaze of white light which was perfectly surprising; on examination it appeared that the whole of the inside of the bark of the log was covered with a white byssoid mycelium of a peculiarly strong smell, but unfortunately in such a state that the perfect form could not be ascertained. This was luminous, but the light was by no means so bright as in those parts of the wood where the spawn had penetrated more deeply, and where it was so intense that the roughest treatment scarcely seemed to check it. If any attempt was made to rub off the luminous matter it only shone the more brightly, and when wrapped up in five folds of paper the light penetrated through all the folds on either side as brightly as if the specimen was exposed; when, again, the specimens were placed in the pocket, the pocket when opened was a mass of light. The luminosity had now been going on for three days. Unfortunately we did not see it ourselves till the third day, when it had, possibly from a change in the state of electricity, been somewhat impaired, but it was still most interesting, and we have merely recorded what we saw ourselves. It was almost possible to read the time on the face of a watch, even in its less luminous condition. We do not for a moment suppose that the mycelium is essentially luminous, but are rather inclined to believe that a peculiar occurrence of climatic conditions is necessary for the production of the phenomenon, which is certainly one of great rarity. Observers as we have been of fungi in their native haunts for fifty years, it has never fallen to our lot to witness a similar case before, though Professor Churchill Babington once sent us specimens of luminous wood, which had, however, lost their luminosity before they arrived. It should be observed that the parts of the wood which were most luminous were not only deeply penetrated by the more delicate parts of the mycelium, but were those which were most decomposed. It is probable, therefore, that this fact is an element in the case as well as the presence of fungoid matter."
Another incomplete fungus growth is that called Rhizomorpha subterranea, which extends underneath the soil in long strings in the neighbourhood of old tree stumps, those of oak especially, which are becoming rotten, and upon these it is fixed by its branches. These are cylindrical, very flexible, branching and clothed with a hard bark, encrusting and fragile, at first smooth and brown, becoming later very rough and black. The interior tissue, at first whitish, afterwards of a more or less deep brown colour, is formed of long parallel filaments. The phenomena of luminosity in these fungi have been made the subject of investigation by M. Tulasne. "On the evening of the day when I received the specimens," he writes, "the temperature being about 22° C., all the young branches brightened with an uniform phosphoric light the whole of their length; it was the same with the surface of some of the older branches, the greater number of which were still brilliant in some parts, and only on their surface. I split and lacerated many of these twigs, but their internal substance remained dull. The next evening, on the contrary, this substance having been exposed to contact with the air, exhibited at its surface the same brightness as the bark of the branches. Prolonged friction of the luminous surfaces reduced the brightness and dried them to a certain degree, but did not leave on the fingers any phosphorescent matter."