Chapter 12

Recently an extraordinary instance of luminosity was recorded as occurring in our own country.[H] "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 observed 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 concurrence 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 Prof. 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."

In all cases of phosphorescence recorded, the light emitted is described as of the same character, varying only in intensity. It answers well to the name applied to it, as it seems remarkably similar to the light emitted by some living insects and other animal organisms, as well as to that evolved, under favourable conditions, by dead animal matter--a pale bluish light, resembling that emitted by phosphorus as seen in a dark room.

Another phenomenon worthy of note is the change of colour which the bruised or cut surface of some fungi undergo. Most prominent amongst these are certain poisonous species of _Boletus_, such, for instance, as _Boletus luridus_, and some others, which, on being bruised, cut, or divided, exhibit an intense, and in some cases vivid, blue. At times this change is so instantaneous that before the two freshly-cut portions of a _Boletus_ can be separated, it has already commenced, and proceeds rapidly till the depth of intensity has been gained. This blue colour is so universally confined to dangerous species that it is given as a caution that all species which exhibit a blue colour when cut or bruised, should on no account be eaten. The degree of intensity varies considerably according to the condition of the species. For example, _Boletus cærulescens_ is sometimes only very slightly, if at all, tinged with blue when cut, though, as the name implies, the peculiar phenomenon is generally highly developed. It cannot be said that this change of colour has as yet been fully investigated. One writer some time since suggested, if he did not affirm, that the colour was due to the presence of aniline, others have contented themselves with the affirmation that it was a rapid oxidization and chemical change, consequent upon exposure of the surfaces to the air. Archdeacon Robinson examined this phenomenon in different gases, and arrived at the conclusion that the change depends on an alteration of molecular arrangement.[I]

One of the best of the edible species of _Lactarius_, known as _Lactarius deliciosus_, changes, wherever cut or bruised, to a dull livid green. This fungus is filled with an orange milky fluid, which becomes green on exposure to the air, and it is consequently the juice which oxidizes on exposure. Some varieties more than others of the cultivated mushroom become brownish on being cut, and a similar change we have observed, though not recorded, in other species.

The presence of a milky juice in certain fungi has been alluded to. This is by no means confined to the genus _Lactarius_, in which such juice is universal, sometimes white, sometimes yellow, and sometimes colourless. In Agarics, especially in the subgenus _Mycena_, the gills and stem are replete with a milky juice. Also in some species of _Peziza_, as for instance in _Peziza succosa_, B., sometimes found growing on the ground in gardens, and in _Peziza saniosa_, Schrad., also a terrestrial species, the same phenomenon occurs. To this might be added such species as _Stereum spadiceum_, Fr., and _Stereum sanguinolentum_, Fr., both of which become discoloured and bleeding when bruised, while _Corticium lactescens_ distils a watery milk.

Fungi in general have not a good repute for pleasant odours, and yet it must be conceded that they are not by any means devoid of odour, sometimes peculiar, often strong, and occasionally very offensive. There is a peculiar odour common to a great many forms, which has come to be called a fungoid odour; it is the faint smell of a long-closed damp cellar, an odour of mouldiness and decay, which often arises from a process of eremocausis. But there are other, stronger, and equally distinct odours, which, when once inhaled, are never to be forgotten. Amongst these is the fetid odour of the common stinkhorn, which is intensified in the more beautiful and curious _Clathrus_. It is very probable that, after all, the odour of the _Phallus_ would not be so unpleasant if it were not so strong. It is not difficult to imagine, when one encounters a slight sniff borne on a passing breeze, that there is the element of something not by any means unpleasant about the odour when so diluted; yet it must be confessed that when carried in a vasculum, in a close carriage, or railway car, or exposed in a close room, there is no scruple about pronouncing the odour intensely fetid. The experience of more than one artist, who has attempted the delineation of _Clathrus_ from the life, is to the effect that the odour is unbearable even by an enthusiastic artist determined on making a sketch.

Perhaps one of the most fetid of fungi is _Thelephora palmata_. Some specimens were on one occasion taken by Mr. Berkeley into his bedroom at Aboyne, when, after an hour or two, he was horrified at finding the scent far worse than that of any dissecting room. He was anxious to save the specimens, but the scent was so powerful that it was quite intolerable till he had wrapped them in twelve thick folds of the strongest brown paper. The scent of _Thelephora fastidiosa_ is bad enough, but, like that of _Coprinus picaceus_, it is probably derived from the imbibition of the ordure on which it is developed. There needs no stronger evidence that the scent must not only be powerful, but unpleasant, when an artist is compelled, before a rough sketch is more than half finished, to throw it away, and seek relief in the open air. A great number of edible Agarics have the peculiar odour of fresh meal, but two species, _Agaricus odorus_ and _Agaricus fragrans_, have a pleasant anise-like odour. In two or three species of tough _Hydnum_, there is a strong persistent odour somewhat like melilot or woodruffe, which does not pass away after the specimen has been dried for years. In some species of _Marasmius_, there is a decidedly strong odour of garlic, and in one species of _Hygrophorus_, such a resemblance to that of the larva of the goat moth, that it bears the name of _Hygrophorus cossus_. Most of the fleshy forms exhale a strong nitrous odour during decay, but the most powerful we remember to have experienced was developed by a very large specimen of _Choiromyces meandriformis_, a gigantic subterranean species of the truffle kind, and this specimen was four inches in diameter when found, and then partially decayed. It was a most peculiar, but strong and unpleasantly pungent nitrous odour, such as we never remember to have met with in any other substance. _Peziza venosa_ is remarkable when fresh for a strong scent like that of aquafortis.

Of colour, fungi exhibit an almost endless variety, from white, through ochraceous, to all tints of brown until nearly black, or through sulphury yellow to reds of all shades, deepening into crimson, or passing by vinous tints into purplish black. These are the predominating gradations, but there are occasional blues and mineral greens, passing into olive, but no pure or chlorophyllous green. The nearest approach to the latter is found in the hymenium of some _Boleti_. Some of the Agarics exhibit bright colours, but the larger number of bright-coloured species occur in the genus _Peziza_. Nothing can be more elegant than the orange cups of _Peziza aurantia_, the glowing crimson of _Peziza coccinea_, the bright scarlet of _Peziza rutilans_, the snowy whiteness of _Peziza nivea_, the delicate yellow of _Peziza theleboloides_, or the velvety brown of _Peziza repanda_. Amongst Agarics, the most noble _Agaricus muscarius_, with its warty crimson pileus, is scarcely eclipsed by the continental orange _Agaricus cæsarius_. The amethystine variety of _Agaricus laccatus_ is so common and yet so attractive; whilst some forms and species _Russula_ are gems of brilliant colouring. The golden tufts of more than one species of _Clavaria_ are exceedingly attractive, and the delicate pink of immature _Lycogala epidendrum_ is sure to command admiration. The minute forms which require the microscope, as much to exhibit their colour as their structure, are not wanting in rich and delicate tints, so that the colour-student would find much to charm him, and good practice for his pencil in these much despised examples of low life.

Amongst phenomena might be cursorily mentioned the peculiar sarcodioid mycelium of _Myxogastres_, the development of amoeboid forms from their spores, and the extraordinary rapidity of growth, as the well-known instance of the _Reticularia_ which Schweinitz observed running over iron a few hours after it had been red hot. Mr. Berkeley has observed that the creamy mycelium of _Lycogala_ will not revive after it has become dry for a few hours, though so active before.

[A] M. J. Berkeley, "Introduction to Cryptogamic Botany," p. 265.

[B] Tulasne, "Sur la Phosphorescence des Champignons," in "Ann. des Sci. Nat." (1848), vol. ix, p. 338.

[C] In "Hooker's Journal of Botany" (1840), vol. ii. p. 426.

[D] Berkeley, "Introduction to Crypt. Bot." t. 265.

[E] Dr. Collingwood, in "Journal of Linnæan Society (Botany)," vol. x. p. 469.

[F] In "Hooker's Journal of Botany" for April, 1842.

[G] Tulasne, "Sur la Phosphorescence," in "Ann. des Sci. Nat." (1848), vol ix. p. 340, &c.

[H] Rev. M. J. Berkeley, in "Gardener's Chronicle" for 1872, p. 1258.

[I] Berkeley, "Introduction to Crypt. Bot." p. 266.

VI.

THE SPORE AND ITS DISSEMINATION.

A work of this character would hardly be deemed complete without some reference to the above subject, which has moreover a relation to some of the questions discussed, and particularly of spore diffusion in the atmosphere. The largest spore is microscopic, and the smallest known scarcely visible under a magnifying power of 360 diameters. Taking into account the large number of species of fungi, probably scarcely less numerous than all the flowering plants, and the immense number of spores which some of the individuals produce, they must be exceedingly plentiful and widely diffused, though from their minuteness not easy to be discerned. It has been attempted to estimate the number of spores which might be produced by one single plant of _Lycoperdon_, but the number so far exceeds that which the mind is accustomed to contemplate that it seems scarcely possible to realize their profusion. Recent microscopic examinations of the common atmosphere[A] show the large quantity of spores that are continually suspended. In these investigations it was found that spores and similar cells were of constant occurrence, and were generally present in considerable numbers. That the majority of the cells were living, and ready to undergo development on meeting with suitable conditions, was very manifest, as in those cases in which preparations were retained under observation for any length of time, germination rapidly took place in many of the cells. In few instances did any development take place, beyond the formation of networks of mycelium, or masses of toruloid cells, but, in one or two, distinct sporules were developed on the filaments arising from some of the larger septate spores; and in a few others, _Penicillium_ and _Aspergillus_ produced their characteristic heads of fructification. With regard to the precise nature of the spores, and other cells present in various instances, little can be said, as, unless their development were to be carefully followed out through all its stages, it is impossible to refer them to their correct species or even genera. The greater number of them are apparently referable to the old orders of fungi, _Sphæronemei_, _Melanconei_, _Torulacei_, _Dematiei_ and _Mucedines_, while some probably belonged to the _Pucciniæi_ and _Cæomacei_.

Hence it is demonstrated that a large number of the spores of fungi are constantly present in the atmosphere, which is confirmed by the fact that whenever a suitable pabulum is exposed it is taken possession of by floating spores, and soon converted into a forest of fungoid vegetation. It is admitted that the spores of such common moulds as _Aspergillus_ and _Penicillium_ are so widely diffused, that it is almost impossible to exclude them from closed vessels, or the most carefully guarded preparations. Special contrivances for the dispersion of the spores in the different groups follow a few general types, and it is only rarely that we meet with any method that is confined only to a species or genus. Some of the more significant forms of spores may be illustrated, with their modes of dissemination.

BASIDIOSPORES is a term which we may employ here to designate all spores borne at the tips of such supports as are found in the _Hymenomycetes_ and _Gasteromycetes_, to which the name of basidia has been given. In fact, under this section we may include all the spores of those two orders, although we may be ignorant of the precise mode in which the fruit of most of the _Myxogastres_ is developed. Guarding ourselves at the outset against any misinterpretation as to the use of this term, which, in fact, we employ simply to designate the fruit of _Hymenomycetes_, we may have excuse in our desire to limit special terms as much as possible. In the _Agaricini_ the spores are plentiful, and are distributed over the hymenium or gill plates, the surface of which is studded with basidia, each of which normally terminates with four short, erect, delicate, thread-like processes, each of which is surmounted by a spore. These spores are colourless or coloured, and it is upon this fact that primary divisions in the genus _Agaricus_ are based, inasmuch as colour in the spores appears to be a permanent feature. In white-spored species the spores are white in all the individuals, not mutable as the colour of the pileus, or the corolla in phanerogamic plants. So also with the pink spored, rusty spored, black spored, and others. This may serve to explain why colour, which is so little relied upon in classification amongst the higher plants, should be introduced as an element of classification in one of the largest genera of fungi.

There are considerable differences in size and form amongst the spores of the _Agaricini_, although at first globose; when mature they are globose, oval, oblong, elliptic, fusiform, and either smooth or tuberculated, often maintaining in the different genera or subgenera one particular characteristic, or typical form. It is unnecessary here to particularize all the modifications which the form and colour of the spores undergo in different species, as this has already been alluded to. The spores in the _Polyporei_, _Hydnei_, &c., are less variable, of a similar character, as in all the _Hymenomycetes_, except perhaps the _Tremellini_.

When an Agaric is mature, if the stem is cut off close to the gills, and the pileus inverted, with the gills downwards on a sheet of black paper (one of the pale-spored species is best for this purpose), and left for a few hours, or all night, in that position, the paper will be found imprinted in the morning with a likeness of the under side of the pileus with its radiating gills, the spores having been thrown down upon the paper in such profusion, from the hymenium, and in greater numbers from the opposed surfaces of the gills. This little experiment will be instructive in two or three points. It will illustrate the facility with which the spores are disseminated, the immense number in which they are produced, and the adaptability of the gill structure to the economy of space, and the development of the largest number of basidiospores from a given surface. The tubes or pores in _Polyporei_, the spines in _Hydnei_, are modifications of the same principles, producing a like result.

In the _Gasteromycetes_ the spores are produced in many cases, probably in most, if not all, at the tips of sporophores; but the hymenium, instead of being exposed, as in the _Hymenomycetes_, is enclosed within an outer peridium or sac, which is sometimes double. The majority of these spores are globose in form, some of them extremely minute, variously coloured, often dark, nearly black, and either externally smooth or echinulate. In some genera, as _Enerthenema_, _Badhamia_, &c., a definite number of spores are at first enclosed in delicate cysts, but these are exceptions to the general rule: this also is the case in at least one species of _Hymenogaster_. As the spores approach maturity, it may be observed in such genera as _Stemonitis_, _Arcyria_, _Diachea_, _Dictydium_, _Cribraria_, _Trichia_, &c., that they are accompanied by a sort of reticulated skeleton of threads, which remain permanent, and served in earlier stages, doubtless, as supports for the spores; being, in fact, the skeleton of the hymenium. It has been suggested that the spiral character of the threads in _Trichia_ calls to mind the elaters in the _Hepaticæ_, and like them may, by elasticity, aid in the dispersion of the spores. There is nothing known, however, which will warrant this view. When the spores are mature, the peridium ruptures either by an external orifice, as in _Geaster_, _Lycoperdon_, &c., or by an irregular opening, and the light, minute, delicate, spores are disseminated by the slightest breath of air. Specimens of _Geaster_ and _Bovista_ are easily separated from the spot on which they grew; when rolling from place to place, the spores are deposited over a large surface. In the _Phalloidei_ the spores are involved in a slimy mucus which would prevent their diffusion in such a manner. This gelatinous substance has nevertheless a peculiar attraction for insects, and it is not altogether romantic to believe that in sucking up the fetid slime, they also imbibe the spores and transfer them from place to place, so that even amongst fungi insects aid in the dissemination of species. Whether or not the _Myxogastres_ should be included here is matter of opinion, since the mode in which the spores are developed is but little known; analogy with the _Trichogastres_ in other points alone leading to the conclusion that they may produce basidiospores. The slender, elastic stems which support the peridia in many species are undoubted aids to the dissemination of the spores.[B]