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produced by the bursting of the pollen granules at the moment of fructification. (Zavadsky.) Ingenhouss, Senebier, and Saussure never observed this luminous appearance in Trapaeolum majus; neither could L. Treviranus discover it in Tagetes and other flowers; hence he regards the phenomenou as a mere illusion produced by the yellow colour of the flowers, which at night gives them an appearance of peculiar brightness.

Of a different nature from this is the flame observed by Ingenhouss, Bertholon, and Willdenow around the flowers of Dictamnus albus on the approach of a lighted candle—an appearance however which Schrank, Th. Saussure, Sprengel, and Treviranus were never able to discover. Biot (Ann. Chim. Phys. 50, 386) attributes this flame to the combustion of a volatile oil contained in the cells of the flower-stalks.

2. Steady Phosphorescence. Some plants emit in the dark a faint continuous light, probably resulting from the formation of some substance which burns and emits light at ordinary temperatures, and consists, not of phosphorus, but more probably of a compound containing carbon and hydrogen.

The leaves of Phytolacea decandra have been observed to shine in September from 9 till 12 o'clock at night, sometimes with bluish green, sometimes with yellowish green light, accordingly as the current of air was stronger or weaker: they also remained luminous after being wiped. (K. v. Szäts A. Tr. 8, 2, 54.)

The acrid, milky juice of Cipó de Cananam (a plant growing in Brazil and probably belonging to the genus Euphorbia) emits light for several seconds when it flows from a wound in the plant. (Mornay, Gilb. 56, 367.)

Rhizomorpha subterranea stellata and aidalea, which grow in mines, emit light from their whole surfaces, but especially from the whitish growing points. The luminosity is brighter in young plants than in old ones; brighter also when they grow in warm, damp parts of the mine than in dry, cold situations: it is also increased when the plants are heated to 40° C. Rhizomorphs shine more brightly in oxygen gas than in common air. When they are immersed in this gas, together with a little water, they often continue luminous for nine days; and the oxygen gas is then found to be nearly consumed and converted into a somewhat smaller volume of carbonic acid. When these plants in the moist state bave ceased to shine in the air, their luminosity cannot be restored by electric sparks or by oxygen gas: but it may often be restored by moistening the plant, when its cessation has been caused by dryness. The phosphorescence ceases in vacuo, but reappears when the air is admitted, even if the plant has remained in the vacuum for two hours. The plant likewise ceases to shine when placed in nitrogen gas, but regains its luminosity on being brought out into the air. In hydrogen, carbonic oxide, or chlorine gas, on the contrary, it loses its luminosity for ever, so that no light is emitted even when the plant is afterwards immersed in oxygen gas. (Bischof: Comp. Schw. 44, 65; also Laroche, Verh. d. Ges. naturf. Fr. Berlin, 1824, 1, 22.)

Rhizomorpha pinnata has been seen by Friesleben to emit light.

According to Linnaeus, light is emitted by Byssus phosphorea (L) or Dematium violaceum. Pers.

According to Funk and Brandenburg, Schistostega osmundacea, a plant which grows in caverns, is phosphorescent. This is supposed by

Von Esenbeck to be the same moss which Gilbert (Gilb. 30, 242) saw shining with an emerald-green coloured light in a cavern in the Hartz.

According to Ducluzeau, many confervæ growing near Montpelier are phosphorescent.

(6.) Phosphorescence of Putrefying Organic Bodies. Many organic bodies emit light after death, sometimes before the commencement of actual putrefaction, sometimes simultaneously with it.

1. Phosphorescence of Putrefying Animals. At a certain temperature, and in contact with moisture and oxygen gas, a decomposition appears to arise in many dead animals, especially in sea-fish, before the commencement of actual putrefaction,-producing a glutinous substance, whose constituents are capable of burning in the smallest quantity of oxygen, with a feeble light and scarcely perceptible development of heat :-or may it not be supposed that the decomposition is attended by the production of luminous infusoria?

Human corpses are very rarely phosphorescent. Of a body received on the 14th of February and dissected, one of the lower extremities, which remained over, began to exhibit phosphorescence on the 3rd of March. A second body brought into the same dissecting-room on the 5th of March likewise appeared luminous after a few days, first on the external and internal surface of the thorax, then on the abdomen, bones, tendons, and membranes, more faintly on the muscles, not at all on the viscera of the thorax. A portion of this second body laid upon a third rendered this also phosphorescent in two days, as if by contagion. The luminous matter, which appeared to be of an oily nature, could be removed in many places by the finger, on which it continued to shine. Placed under the microscope, it illuminated the whole field of view, and appeared to be in motion, like gamboge touched with water; but no animalcules were visible, excepting a minute Vibrio, such as is often observed in macerated bodies. The luminous substance continued to shine brightly in oxygen, carbonic oxide, phosphuretted hydrogen, and nitrogen gas—more faintly in carbonic acid-also with various degrees of brightness under water, milk and oil,- lost its phosphorescent power in a vacuum, but recovered it when the air was re-admitted,—and was finally extinguished in sulphuretted hydrogen and chlorine gas, hot air, boiling water and alcohol. (A. Cooper and Appleton.)

Phosphorescence has likewise been observed in the flesh of oxen, calves, wethers, lambs, pigs, fowls, eagles, swallows, and serpents (Fabr. ab. Aquapendente, Boyle, Beale): in the case of ox-flesh, the phosphorescence ceased when actual putrefaction set in. (Bartholinus.) . At Orleans in 1780, all the meat in a butcher's shop became phosphorescent. Veal, in October, three days old, cut up and beaten soft, but not yet stinking, emitted at a temperature between 12° and 18° C. a white light like phosphorus—was covered with a glutinous substance—imparted its luminous property to the fingers for a short time—continued to shine 24 hours later, at which time it began to smell badly—and even retained its luminosity, though feebly and only in particular places, after 48 hours, when the stench was much more powerful. (Buchner.)—Hen's eggs have also, on one occasion, been seen to emit light when opened.

Hulme produced phosphorescence in some very young tadpoles by preserving them in a solution of common salt and sulphate of soda. Phosphorescence is also exhibited by Sepia officinalis, Loligo, and other species (in Sepia of, according to Spallanzani, the light does not attain its greatest intensity till putrefaction is completely set up);—according to Lenckart, by dead Aplysiæ, various species of Doris and Holothuria; according to Tiedemann, by dead sea-stars; according to Redi, by a Taenia ; according to Redi, Spallanzani and Tilesius by medusas 24 hours after death; and according to an observation of Leo Allatius, by the refise of dead crabs.

Luminosity is most readily exhibited by sea-fish, viz. Squalus Spinax and Pristis ; Tetrodon Mola; Muraená Helena; Gadus A eglefnus; Morhua Merlangus and virens ; Coryphaena Hippurus, Cottus Scorpius and cataphractus, Pleuronectes Platessa; Scomber Scomber and Pelamis; Perca marina; Trigla volilans; Clupea Harengas; Salmo Salar and Trutta. Freshwater fish may, with some difficulty, be made to emit light, by rubbing them with salt and laying them in a moderately warm place. Heinrich, after many fruitless attempts, succeeded by this process in making the Esox lucius emit a very beautiful light, and the Silurus Glanis a faint light.

Phosphorescence shows itself in a day or two after the death of the fish, provided they are kept, neither boiled nor salted, in a moist condition, at a temperature of about 12° to 18° C. and in contact with air or oxygen

On the contrary, no phosphorescence is produced either in carbonic acid or sulphuretted hydrogen gas, or again when the fish are kept from contact of air by packing—in which case they may in winter be brought to the phosphorescent state by exposure to the air after they have been kept for fourteen days; e. g. Shell-fish. (Henrich.)

Phosphorescence begins at the head of the fish, particularly about the eyes, then extends to the belly, and lastly to the tail. (Martin, Schwed. Åbhandl. 23, 224.) According to Dessaignes, the luminosity is most conspicuous on the aponeuroses, ligaments, capsules, and milts,—in short on the gelatinous parts, not on those of muscular structure. The internal parts do not emit light till they have been exposed to the air for a time. Sometimes there exudes from the animals a glutinous liquid, which is at first clear, but afterwards becomes thick and turbid, and then luminous. (Dessaignes.) This luminous slime may be spread upon the fingers and other foreign bodies. Hulme made a luminous solution of this substance in fresh water, sea-water, or a dilute solution of common salt, Glauber's salt, or sulphate of magnesia, by immersing the flesh of herrings or whitings in these liquids ; after three days a luminous ring formed on the surface; when agitated, the whole mass of liquid became phosphorescent, and often continued so for several days.

According to Hulme, no rise of temperature is observable during the phosphorescence. According to Dessaignes, the phenomenon is accompanied by formation of carbonic acid iv the air.

A freezing temperature interrupts the phosphorescence; a slight rise of temperature increases it; a boiling heat destroys it for ever. (Hulme.)

- Abstraction of water destroys the luminosity of the fish; e.g. if it bé suspended in a vessel containing quick lime. (Dessaignes.) The action of saturated solutions of various salts, alkalis, sulphuret of potassium, acids, alcohol, and ether may perhaps be similar; nevertheless, their lightdestroying power may also proceed from another cause—since dilute acids, even carbonic and hydrosulphuric acid, and likewise lime-water, destroy the phosphorescence. (Hulme.) The luminosity is increased in intensity, but shortened in duration, by dilute solutions of common salt, Glauber's

salt

, phosphate of soda, sulphate of magnesia, nitre, sugar, and honey. (Hulme.) According to Hulme, a luminous fish diminishes in brightness when placed in a vacuum; according to Dessaignes, it ceases to shine in vacuo, but regains its luminosity when the air is re-admitted. In nitrogen, hydrogen, carbonic acid, and sulphuretted hydrogen gas, the fish continues to shine for a short time only. (Dessaignes, Hulme.). In boiled water or sea-water, it soon ceases to shine when the air is' kept from it; but if air-bubbles make their appearance, the phosphorescence re-appears, and continues for a time proportionate to the quantity of air present. În ordinary fat oil, the fish continues to shine for 24 hours: but if the oil has been boiled, the light ceases as soon as the fish is put into it. (Dessaignes.)

The fish, when left to itself, continues phosphorescent for some days until fetid putrefaction ensues, and then the light disappears.

2. Phosphorescence of Putrefying Plants. The complete decay of the various parts of a plant is also when the temperature is moderate, and moisture and a small qnantity of air are present-at times accompanied by a peculiar decomposition, resulting in the development of a substance which, like phosphorus, burns at ordinary temperatures, producing light and a small quantity of heat. Nevertheless, this substance cannot be phosphorus (especially in wood which does not contain that element), but must rather be considered as a peculiar, and easily combustible compound of carbon, hydrogen, and oxygen, resulting from the decomposition of the original proximate constituents of the plant.

The phosphorescence is chiefly conspicuous in wood, as well in that of the root, as in that of the stem and branches. The phosphorescence has been observed in the wood of Quercus Robur; Fagus Castanea and sylvatica; Betula alba and Alnus; Corylus Avellana; Pinus Abies, Strobus, picea and sylvestris; Juglans regia; and some species of willow.

The decomposition of the wood must take place in a situation where but a moderate quantity of moisture is present, and the air is almost excluded, in which case, the wood will remain white; when there is much moisture and free access of air, it is reduced to a brown pulverulent mass which is not luminous. Phosphorescent wood is often but little decomposed, and retains a great deal of its hardness. (Heinrich.) John (Schw. 14, 415) saw light emitted by splinters of wood from a newly felled pine. Old wooden pipes often exhibit phosphorescence when taken out of the ground. When roots, which have been dead for some years, are taken out of the earth and kept in a moderately damp place, they often become phosphorescent after a few days. (Heinrich.)— According to Dessaignes, the phosphorescence ceases when the temperature falls to + 6° C (42.8° Fah.); according to Heinrich, it shows itself even at 0° C. fainter indeed, but more durable, continuing for more than fifteen days. By boiling water it is irrecoverably destroyed. Wood heated in the air to the boiling point of water recovers its luminosity by immersion in cold water. (Heinrich.) Wood loses its phosphorescent properties by drying; wood which when exposed to the air ceases to emit light after two or three days, remains luminous for fourteen days when wrapped up in moist blotting-paper (Heinrich). In a vessel containing quick-lime it soon ceases to shine (Dessaignes); but by moderately wetting it, the phosphorescence may to a certain extent be restored.

Wood does not shine for a longer time or with greater intensity in oxyen gas than in common air (Heinrich, Dessaignes); according to Böckman and Gärtner, it does not shine more brightly but longer; according to Spallanzani, it shines with greater brightness. According to Dessaignes, the phosphorescence is brighter, but of shorter duration in compressed air. The same observer found that the phosphorescence gradually died away in a vacuum. Heinrich could not produce any decrease of luminosity by rarefying the air. In nitrogen, hydrogen, and phosphuretted hydrogen gas, the wood remains luminous for only a few hours, and then, according to Spallanzani, recovers its luminosity on the re-admission of common air; in fluoride of silicon, chlorine, ammonia, hydrochloric acid, carbonic acid, and sulphuretted hydrogen gas, its phosphorescence ceases in a few minutes, and cannot be wholly restored by contact of air. (Böckmann, Gärtner, Heinrich.)-In unboiled water, fat oil, and mercury, the phosphorescence ceases after an interval varying from 6 to 24 hours; sooner in alcohol, ether, boiled oil, lime-water, solution of sulphuret of potassium, dilute acids, and saline solutions; instantly in sulphuric acid. Saturated solutions of sal-ammoniac, nitre, and common salt, produce at first an increase of luminosity. (Gärtner, Heinrich, Dessaignes.)

The phosphorescence of wood in air or oxygen gas is attended with consumption of oxygen and production of carbonic acid without perceptible diminution of volume. (Dessaignes.) Air pumped out of decaying wood contains a little oxygen with a great deal of carbonic acid gas. (Dessaignes.) Hence may be explained the fact that wood continues to emit light, even in media which contain no oxygen, provided they do not exert a destructive action on the phosphorescent matter.

Potatoes kept in a cellar till they began to germinate, were, in one instance, observed to emit light on being cut open. (J. Phys. 33, 225; also Gren. J. d. Phys. 2, 420.)—Kortum (Voigt, n. Nag. 2. 67) frequently observed phosphorescence in valerian roots while yet tolerably fresh. Fresh tormentilla roots gathered in August have been seen to emit light, particularly on those parts where the last year's nodosities were situated. (Berl. Jahrb. 1, 174.) -—Likewise gourds, mushrooms, and turf are said to be sometimes phosphorescent.

Göbel (Schw. 40, 257) allowed some raspberry juice mixed with sugar to ferment in a cask, into the bung-hole of which was inserted a glass tube 1 inch wide and 3 feet long, filled with the same juice, so that the carbonic acid gas developed by the fermentation was compelled to escape through the tube. The bubbles of gas which thus ascended continued to exhibit phosphorescence for more than an hour. The light of the bubbles was strongest just as they passed from the cask into the tube, diminished in intensity as they ascended, and disappeared completely when they came in contact with the air. When the gas was collected by means of a gas-delivery tube adapted to the tube above mentioned, it was no longer phosphorescent, had no smell, and exhibited with ammonia the reaction of pure carbonic acid. (Göbel and Schweigger suggest that the development of light in this experiment may be due to electricity: but it is possible that the carbonic acid gas may have been mixed with a very small quantity of a volatile and combustible organic matter produced by the fermentation, and that this substance may have been burnt with development of light, by combining with the oxygen of the air probably held in solution by the juice of the tube, before the bubbles reached the top of the tube.)

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