The _Physomycetes_ consist of two orders, _Antennariei_ and _Mucorini_, which differ from each other almost as much in habitat as in external appearance. The former, if represented by _Antennaria_, runs over the green and fading leaves of plants, forming a dense black stratum, like a congested layer of soot; or in _Zasmidium_, the common cellar fungus, runs over the walls, bottles, corks, and other substances, like a thick sooty felt. In the _Mucorini_, as in the _Mucedines_, there is usually less restriction to any special substance. _Mucor mucedo_ occurs on bread, paste, preserves, and various substances; other species of _Mucor_ seem to have a preference for dung, and some for decaying fungi, but rotting fruits are nearly sure to support one or other of the species. The two known species of the curious genus _Pilobolus_, as well as _Hydrophora_, are confined to dung. _Sporodinia_, _Syzygites_, &c., nourish on rotten Agarics, where they pa.s.s through their somewhat complicated existence.

The _Ascomycetes_ contain an immense number of species, and in general terms we might say that they are found everywhere. The _Tuberacei_ are subterraneous, with a preference for calcareous districts. The _Perisporiacei_ are partly parasitical and partly not. The _Erysiphei_ include those of the former which flourish at the expense of the green parts of roses, hops, maples, poplars, peas, and many other plants, both in Europe and in North America, whilst in warmer lat.i.tudes the genus _Meliola_ appears to take their place.

The _Elvellacei_ are fleshy fungi, of which the larger forms are terrestrial; _Morch.e.l.la_, _Gyromitra_, and _Helvella_ mostly growing in woods, _Mitrula_, _Spathularia_, and _Leotia_ in swampy places, and _Geoglossum_ amongst gra.s.s. The very large genus _Peziza_ is divided into groups, of which _Aleuriae_ are mostly terrestrial. This group includes nearly all the large-sized species, although a few belong to the next. _Lachneae_ are partly terrestrial and partly epiphytal, the most minute species being found on twigs and leaves of dead plants. In _Phialea_ the species are nearly entirely epiphytal, as is also the case in _Helotium_ and allied genera. Some species of _Peziza_ are developed from the curious ma.s.ses of compact mycelium called _Sclerotia_. A few are rather eccentric in their habitats. _P.

viridaria_, _P. domestica_, and _P. hoemastigma_, grow on damp walls; _P. granulata_ and some others on dung. _Peziza Bullii_ was found growing on a cistern. _P. theleboloides_ appears in profusion on spent hops. _P. episphaeria_, _P. clavariarum_, _P. vulgaris_, _Helotium pruinosum_, and others are parasitic on old fungi. One or two species of _Helotium_ grow on submerged sticks, so as to be almost aquatic, a circ.u.mstance of rare occurrence in fungi. Other _Discomycetes_ are similar in their habitats to the _Elvellacei_. The group to which the old genus _Ascobolus_ belongs is in a great measure confined to the dung of various animals, although there are two or three lignicolous species; and _Ascopha.n.u.s saccharinus_ was first found on old leather, _Ascopha.n.u.s testaceus_ on old sacking, &c. _Ascomyces_ is, perhaps, the lowest form which ascomycetous fungi a.s.sume, and the species are parasitic on growing plants, distorting the leaves and fruit, const.i.tuting themselves pests to the cultivators of peach, pear, and plum trees.

The _Sphaeriacei_ include a very large number of species which grow on rotten wood, bark, sticks, and twigs; another group is developed on dead herbaceous stems; yet another is confined to dead or dying leaves. One genus, _Torrubia_, grows chiefly on insects; _Hypomyces_ is parasitic on dead fungi; _Claviceps_ is developed from ergot, _Poronia_ on dung, _Polystigma_ on living leaves, as well as some species of _Stigmatea_ and _Dothidea_. Of the genus _Sphaeria_, a considerable number are found on dung, now included by some authors under _Sordaria_ and _Sporormia_, genera founded, as we think, on insufficient characters. A limited number of species are parasitic on lichens, and one species only is known to be aquatic.

[Ill.u.s.tration: FIG. 109.--_Torrubia militaris_ on pupa of a moth.]

We have thus rapidly, briefly, and casually indicated the habitats to which the majority of the larger groups of fungi are attached, regarding them from a systematic point of view. There is, however, another aspect from which we might approach the subject, taking the host or matrix, or in fact the habitat, as the basis, and endeavouring to ascertain what species of fungi are to be found in such positions. This has partly been done by M. Westendorp;[E] but every year adds considerably to the number of species, and what might have been moderately accurate twelve years since can scarcely be so now. To carry this out fully a special work would be necessary, so that we shall be content to indicate or suggest, by means of a few ill.u.s.trations, the forms of fungi, often widely distinct in structure and character, to be found in the same locality.

The stems of herbaceous plants are favourite habitats for minute fungi. The old stems of the common nettle, for example, perform the office of host to about thirty species.[F] Of these about nine are _Pezizae_, and there are as many sphaeriaceous fungi, whilst three species of _Dendryphium_, besides other moulds, select this plant.

Some of these have not hitherto been detected growing on any other stems, such as _Sphaeria urticae_ and _Lophiostoma s.e.x-nucleatum_, to which we might add _Peziza fusarioides_ and _Dendryphium griseum_.

These do not, however, include the whole of the fungi found on the nettle, since others are parasitic upon its living green parts. Of these may be named _aecidium urticae_ and _Peronospora urticae_, as well as two species described by Desmazieres as _Fusisporium urticae_ and _Septoria urticae_. Hence it will be seen how large a number of fungi may attach themselves to one herbaceous plant, sometimes whilst living, but most extensively when dead. This is by no means a solitary instance, but a type of what takes place in many others. If, on the other hand, we select such a tree as the common lime, we shall find that the leaves, twigs, branches, and wood bear, according to M.

Westendorp,[G] no less than seventy-four species of fungi, and of these eleven occur on the leaves. The spruce fir, according to the same authority, nourishes one hundred and fourteen species, and the oak not less than two hundred.

It is curious to note how fungi are parasitic upon each other in some instances, as in that of _Hypomyces_, characteristic of the genus, in which sphaeriaceous fungi make hosts of dead _Lactarii_, &c. We have already alluded to _Nyctalis_, growing on decayed _Russulae_, to _Boletus parasiticus_, flourishing on old _Scleroderma_, and to _Agaricus Loveia.n.u.s_, on the pileus of _Agaricus nebularis_. To these we may add _Torrubia ophioglossoides_ and _T. capitata_, which flourish on decaying _Elaphomyces_, _Stilb.u.m tomentosum_ on old _Trichia_, _Peziza Clavariarum_ on dead _Clavaria_, and many others, the mere enumeration of which would scarcely prove interesting. A very curious little parasite was found by Messrs. Berkeley and Broome, and named by them _Hypocrea inclusa_, which makes itself a home in the interior of truffles. Mucors and moulds flourish on dead and decaying Agarics, and other fleshy forms, in great luxuriance and profusion.

_Mucor ramosus_ is common on _Boletus luridus_, and _Syzygites megalocarpus_ on Agarics, as well as _Acrostalagmus cinnabarinus_. A very curious little parasite, _Echin.o.botryum atrum_, occurs like minute nodules on the flocci of black moulds. _Bactridium Helvellae_ usurps the fructifying disc of species of _Peziza_. A small _Sphinctrina_ is found both in Britain and the United States on old _Polypori_. In _Sphaeria nigerrima_, _Nectria episphaeria_, and two or three others, we have examples of one sphaeriaceous fungus growing upon another.

Mr. Phillips has recently indicated the species of fungi found by him on charcoal beds in Shropshire,[H] but, useful as it is, that only refers to one locality. A complete list of all the fungi which have been found growing on charcoal beds, burnt soil, or charred wood, would be rather extensive. The fungi found in hothouses and stoves are also numerous, and often of considerable interest from the fact that they have many of them never been found elsewhere. Those found in Britain,[I] for instance, are excluded from the British Flora as doubtful, because, growing upon or with exotic plants, they are deemed to be of exotic origin, yet in very few cases are they known to be inhabitants of any foreign country. Some species found in such localities are not confined to them, as _Agaricus coepestipes_, _Agaricus cristatus_, _aethalium vaporarium_, &c. It is somewhat singular that certain species have a predilection for growing in proximity with other plants with which they do not appear to have any more intimate relation. Truffles, for instance, in a.s.sociation with oaks, _Peziza lanuginosa_ under cedar-trees, _Hydnangium carneum_ about the roots of _Eucalypti_, and numerous species of _Agaricini_, which are only found under trees of a particular kind. As might be antic.i.p.ated, there is no more fertile habitat for fungi than the dung of animals, and yet the kinds found in such locations belong to but a few groups. Amongst the _Discomycetes_, a limited number of the genus _Peziza_ are fimicolous, but the allied genus _Ascobolus_, and its own immediate allies, include amongst its species a large majority that are found on dung. If we take the number of species at sixty-four, there are only seven or eight which do not occur on dung, whilst fifty-six are fimicolous. The species of _Sphaeria_ which are found on the same substances are also closely allied, and some Continental authors have grouped them under the two proposed genera _Sporormia_ and _Sordaria_, whilst f.u.c.kel[J] proposes a distinct group of _Sphaeriacei_, under the name of _Fimicoli_, in which he includes as genera _Coprolepa_, _Hypocopra_, _Delitschia_, _Sporormia_, _Pleophragmia_, _Malinvernia_, _Sordaria_, and _Cercophora_. The two species of _Pilobolus_, and some of _Mucor_, are also found on dung, _Isaria felina_ on that of cats, _Stilb.u.m fimetarium_ and a few other moulds, and amongst Agarics some species of _Coprinus_. Animal substances are not, as a rule, prolific in the production of fungi.

_Ascobolus saccharinus_ and one or two others have been found upon old leather. _Onygena_ of two or three species occurs on old horn, hoofs, &c. Cheese, milk, &c., afford a few forms, but the largest number infest dead insects, either under the mouldy form of _Isaria_ or the more perfect condition of _Torrubia_, and occasionally under other forms.

Robin[K] has recorded that three species of _Brachinus_, of the order Coleoptera, have been found infected, whilst living, with a minute yellow fungus which he calls _Laboulbenia Rougeti_, and the same species has been noted on other beetles. _Torrubia Melolonthae_[L] has been described by Tulasne as occurring on the maybug or c.o.c.kchafer, which is allied to, if not identical with, _Cordyceps Ravenelii_, B.

and C., and also that described and figured by M. Fougeroux de Bondaroy.[M] _Torrubia curculionum_, Tul., occurs on several species of beetles, and seems to be by no means uncommon in Brazil and Central America. _Torrubia coespitosa_, Tul., which may be the same as _Cordyceps Sinclairi_, B.,[N] is found on the larvae of _Orthoptera_ in New Zealand, _Torrubia Miquelii_ on the larvae of _Cicada_ in Brazil, and _Torrubia sobolifera_ on the pupae of _Cicada_ in the West Indies.

A romantic account is given of this in an extract cited by Dr. Watson in his communication to the Royal Society.[O] "The vegetable fly is found in the island Dominica, and (excepting that it has no wings) resembles the drone, both in size and colour, more than any other English insect. In the month of May it buries itself in the earth and begins to vegetate. By the latter end of July, the tree is arrived at its full growth, and resembles a coral branch, and is about three inches high, and bears several little pods, which, dropping off, become worms, and from thence flies, like the English caterpillar."

_Torrubia Taylori_, which grows from the caterpillar of a large moth in Australia, is one of the finest examples of the genus. _Torrubia Robertsii_, from New Zealand, has long been known as attacking the larva of _Hepialus virescens_. There are several other species on larvae of different insects, on spiders, ants, wasps, &c., and one or two on mature Lepidoptera, but the latter seem to be rare.

That fungi should make their appearance and flourish in localities and conditions generally considered inimical to vegetable life is no less strange than true. We have already alluded to the occurrence of some species on spent tan, and some others have been found in locations as strange. We have seen a yellow mould resembling _Sporotrichum_ in the heart of a ball of opium, also a white mould appears on the same substance, and more than one species is troublesome in the opium factories of India. A mould made its appearance some years since in a copper solution employed for electrotyping in the Survey Department of the United States,[P] decomposing the salt, and precipitating the copper. Other organisms have appeared from time to time in various inorganic solutions, some of which were considered destructive to vegetable life, and it is not improbable that some of these organisms were low conditions of mould. It may well occasion some surprise that fungi should be found growing within cavities wholly excluded from the external air, as in the hollow of filberts, and the harder sh.e.l.led nuts of _Guilandina_, in the cavities of the fruit of tomato, or in the interior of an egg. It is scarcely less extraordinary that _Hypocrea inclusa_ should flourish in the interior of a kind of truffle.

From the above it will be concluded that the habitats of fungi are exceedingly variable, that they may be regarded as almost universal wherever decaying vegetable matter is found, and that under some conditions animal substances, especially of vegetable feeders, such as insects, furnish a pabulum for their development.

A very curious and interesting inquiry presents itself to our minds, which is intimately related to this subject of the habitats of fungi.

It shapes itself into a sort of "puzzle for the curious," but at the same time one not unprofitable to think about. How is the occurrence of new and before unknown forms to be accounted for in a case like the following?[Q]

It was our fortune--good fortune as far as this investigation was concerned--to have a portion of wall in our dwelling persistently damp for some months. It was close to a cistern which had become leaky. The wall was papered with "marbled" paper, and varnished. At first there was for some time nothing worthy of observation, except a damp wall--decidedly damp, discoloured, but not by any means mouldy. At length, and rather suddenly, patches of mould, sometimes two or three inches in diameter, made their appearance. These were at first of a snowy whiteness, cottony and dense, just like large tufts of cotton wool, of considerable expansion, but of miniature elevation. They projected from the paper scarcely a quarter of an inch. In the course of a few weeks the colour of the tufts became less pure, tinged with an ochraceous hue, and resembling wool rather than cotton, less beautiful to the naked eye, or under a lens, and more entangled. Soon after this darker patches made their appearance, smaller, dark olive, and mixed with, or close to, the woolly tufts; and ultimately similar spots of a dendritic character either succeeded the olive patches, or were independently formed. Finally, little black b.a.l.l.s, like small pin heads, or grains of gunpowder, were found scattered about the damp spots. All this mouldy forest was more than six months under constant observation, and during that period was held sacred from the disturbing influences of the housemaid's broom and duster.

Curiosity prompted us from the first to submit the mouldy denizens of the wall to the microscope, and this curiosity was increased week by week, on finding that none of the forms found vegetating on nearly two square yards of damp wall could be recognized as agreeing specifically with any described moulds with which we were acquainted. Here was a problem to be solved under the most favourable conditions, a forest of mould indoors, within a few yards of the fireside, growing quite naturally, and all strangers. Whence could these new forms proceed?

The cottony tufts of white mould, which were the first to appear, had an abundant mycelium, but the erect threads which sprang from this were for a long time sterile, and closely interlaced. At length fertile threads were developed in tufts, mixed with the sterile threads. These fruit-bearers were shorter and stouter, more sparingly branched, but beset throughout nearly their whole length with short patent, alternate branchlets. These latter were broadest towards the apex, so as to be almost clavate, and the extremity was beset with two or three short spicules. Each spicule was normally surmounted by an obovate spore. The presence of fertile threads imparted the ochraceous tint above alluded to. This tint was slight, and perhaps would not have been noticed, but from the close proximity of the snow-white tufts of barren threads. The fertile flocci were dec.u.mbent, probably from the weight of the spores, and the tufts were a little elevated above the surface of the matrix. This mould belonged clearly to the _Mucedines_, but it hardly accorded well with any known genus, although most intimately related to _Rhinotrichum_, in which it was placed as _Rhinotrichum lanosum_.[R]

The white mould having become established for a week or two, small blackish spots made their appearance on the paper, sometimes amongst thin patches of the mould, and sometimes outside them. These spots, at first cloudy and indefinite, varied in size, but were usually less than a quarter of an inch in diameter. The varnish of the paper was afterwards pushed off in little translucent flakes or scales, an erect olivaceous mould appeared, and the patches extended to nearly an inch in diameter, maintaining an almost universal circular form. This new mould sometimes possessed a dirty reddish tint, but was commonly dark olive. There could be no mistake about the genus to which this mould belonged; it had all the essential characters of _Penicillium_.

Erect jointed threads, branched in the upper portion in a fasciculate manner, and bearing long beaded threads of spores, which formed a ta.s.sel-like head, at the apex of each fertile thread. Although at first reminded of _Penicillium olivaceum_, of Corda, by the colour of this species, it was found to differ in the spores being oblong instead of globose, and the ramifications of the flocci were different. Unable again to find a described species of _Penicillium_ with which this new mould would agree, it was described under the name of _Penicillium chartarum_.[S]

Almost simultaneously, or but shortly after the perfection of the spores of _Penicillium_, other and very similar patches appeared, distinguished by the naked eye more particularly by their dendritic form. This peculiarity seemed to result from the dwarfed habit of the third fungus, since the varnish, though cracked and raised, was not cast off, but remained in small angular fragments, giving to the spots their dendritic appearance, the dark spores of the fungus protruding through the fissures. This same mould was also found in many cases growing in the same spots amongst _Penicillium chartarum_, but whether from the same mycelium could not be determined.

The distinguishing features of this fungus consist in an extensive mycelium of delicate threads, from which arise numerous erect branches, bearing at the apex dark brown opaque spores. Sometimes the branches were again shortly branched, but in the majority of instances were single. The septate spores had from two to four divisions, many of them divided again by cross septa in the longitudinal direction of the spore, so as to impart a muriform appearance. As far as the structure and appearance of the spores are concerned, they resembled those of _Sporidesmium polymorphum_, under which name specimens were at first published,[T] but this determination was not satisfactory.

The mycelium and erect threads are much too highly developed for a good species of _Sporidesmium_, although the name of _Sporidesmium alternaria_ was afterwards adopted. In fresh specimens of this fungus, when seen _in situ_ by a half-inch objective, the spores appear to be moniliform, but if so, all attempts to see them so connected, when separated from the matrix, failed. On one occasion, a very immature condition was examined, containing simple beaded, hyaline bodies, attached to each other by a short neck. The same appearance of beaded spores, when seen _in situ_, was recognized by a mycological friend, to whom specimens were submitted for confirmation.[U]

The last production which made its appearance on our wall-paper burst through the varnish as little black spheres, like grains of gunpowder.

At first the varnish was elevated by pressure from beneath, then the film was broken, and the little blackish spheres appeared. These were, in the majority of cases, gregarious, but occasionally a few of the spheres appeared singly, or only two or three together. As the whole surface of the damp paper was covered by these different fungi, it was scarcely possible to regard any of them as isolated, or to declare that one was not connected with the mycelium of the others. The little spheres, when the paper was torn from the wall, were also growing from the under surface, flattened considerably by the pressure. The spherical bodies, or perithecia, were seated on a plentiful hyaline mycelium. The walls of the perithecia, rather more carbonaceous than membranaceous, are reticulated, reminding one of the conceptacles of _Erysiphe_, to which the perithecia bear considerable resemblance. The ostiolum is so obscure that we doubt its existence, and hence the closer affinity of the plant to the _Perisporiacei_ than to the _Sphaeriacei_. The interior of the perithecium is occupied by a gelatinous nucleus, consisting of elongated cylindrical asci, each enclosing eight globose hyaline sporidia, with slender branched paraphyses. A new genus has been proposed for this and another similar form, and the present species bears the name of _Orbicula cyclospora_.[V]

The most singular circ.u.mstance connected with this narrative is the presence together of four distinctly different species of fungi, all of them previously unknown and undescribed, and no trace amongst them of the presence of any one of the very common species, which would be supposed to develop themselves under such circ.u.mstances. It is not at all unusual for _Sporocybe alternata_, B., to appear in broad black patches on damp papered walls, but in this instance not a trace was to be found. What were the peculiar conditions present in this instance which led to the manifestation of four new forms, and none of the old ones? We confess that we are unable to account satisfactorily for the mystery, but, at the same time, feel equally unwilling to invent hypotheses in order to conceal our own ignorance.

[A] These predilections must be accepted as general, to which there will be exceptions.

[B] Viviani, "I Funghi d'Italia."

[C] Badham's "Esculent Funguses," Ed. i. pp. 42, 116.

[D] An excellent white Agaric occurs on ant nests in the Neilgherries, and a curious species is found in a similar position in Ceylon.

[E] Westendorp, "Les Cryptogams apres leurs stations naturelles."

[F] Cooke, "On Nettle Stems and their Micro-Fungi," in "Journ.

Quekett Micro. Club," iii. p. 69.

[G] Westendorp, "Les Cryptogams apres leurs stations naturelles,"

1865.

[H] "Gardener's Chronicle," 1874.

[I] W. G. Smith, in "Journ. Botany," March, 1873; Berkeley, in "Grevillea," vol. i. p. 88.

[J] f.u.c.kel, "Symbolae Mycologicae," p. 240.

[K] Robin, "Veget. Parasites," p. 622, t. viii. f. 1, 2.

[L] Tulasne, "Selecta Fung. Carp." iii. p. 12.

[M] "Hist. de l'Acad. des Sciences," 1769. Paris, 1772.

[N] Berkeley, "Crypt. Bot." p. 73; Hooker, "New Zealand Flora," ii.

338.

[O] "Philosophical Transactions," liii. (1763), p. 271.

[P] Berkeley's "Outlines," p. 30.

[Q] "Popular Science Review," vol. x. (1871), p. 25.

[R] Specimens of this mould were distributed in Cooke's "Fungi Britannici Exsiccati," No. 356, under the name of _Clinotrichum lanosum_.

[S] Cooke's "Handbook of British Fungi," p. 602.

[T] Cooke's "Fungi Britannici Exsiccati," No. 329, under the name of _Sporidesmium polymorphum_ var. _chartarum_.

[U] This reminds one of Preuss's _Alternaria_, figured in Sturm's "Flora;" it has been suggested that the mould, as seen when examined under a power of 320 diam., is very much like a _Macrosporium_. Again arises the question of the strings of spores attached end to end.