Part 32

It will be seen from the above summary how unsatisfactory it must be to give anything like a general view of the geographical distribution of fungi, or to estimate at all approximately the number of species on the globe. Any attempt, therefore, must be made and accepted subject to the limitations we have expressed.

The conditions which determine the distribution of fungi are not precisely those which determine the distribution of the higher plants. In the case of the parasitic species they may be said to follow the distribution of their foster-plants, as in the case of the rust, smut, and mildew of the cultivated cereals, which have followed those grains wherever they have been distributed, and the potato disease, which is said to have been known in the native region of the potato plant before it made its appearance in Europe. We might also allude to Puccinia malvacearum, Ca., which was first made known as a South American species; it then travelled to Australia, and at length to Europe, reaching England the next year after it was recorded on the Continent. In the same manner, so far as we have the means of knowing, Puccinia Apii, Ca., was known on the Continent of Europe for some time before it was detected on the celery plants in this country. Experience seems to warrant the conclusion that if a parasite affects a certain plant within a definite area, it will extend in time beyond that area to other countries where the foster-plant is found. This view accounts in some part for the discovery of species in this country, year after year, which had not been recorded before; some allowance being made for the fact that an increased number of observers and collectors may cause the search to be more complete, yet it must be conceded that the migration of Continental species must to some extent be going on, or how can it be accounted for that such large and attractive fungi as Sparassis crispa, Helvellas gigas, and Morchella crassipes had never been recorded till recently, or amongst parasitic species such as the two species of Puccinia above named? In the same manner it is undoubtedly true that species which at one time were common gradually become somewhat rare, and at length nearly extinct. We have observed this to apply to the larger species as well as to the microscopic in definite localities. For instance, Craterellus cornucopioides some ten years ago appeared in one wood, at a certain spot, by hundreds, whereas during the past three or four years we have failed to find a single specimen. As many years since, and in two places, where the goat's-beard was abundant, as it is now, we found nearly half the flowering heads infested with Ustilago receptaculorum, but for the past two or three years, although we have sought it industriously, not a single specimen could be found. It is certain that plants found by Dickson, Bolton, and Sowerby, have not been detected since, whilst it is not improbable that species common with us may be very rare fifty years hence. In this manner it would really appear that fungi are much more liable than flowering plants to shift their localities, or increase and diminish in number.

The fleshy fungi, Agaricini and Boleti especially, are largely dependent upon the character of woods and forests. When the undergrowth of a wood is cleared away, as it often is every few years, it is easy to observe a considerable difference in the fungi. Species seem to change places, common ones amongst a dense undergrowth are rare or disappear with the copsewood, and others not observed before take their place. Some species, too, are peculiar to certain woods, such as beech woods and fir woods, and their distribution will consequently depend very much on the presence or absence of such woods. Epiphytal species, such as Agaricus ulmarius, Agaricus mucidus, and a host of others, depend on circumstances which do not influence the distribution of flowering plants. It may be assumed that such species as flourish in pastures and open places are subject to fewer adverse conditions than those which affect woods and forests.

Any one who has observed any locality with reference to its Mycologic Flora over a period of years will have been struck with the difference in number and variety caused by what may be termed a "favourable season," that is, plenty of moisture in August with warm weather afterwards. Although we know but little of the conditions of germination in Agarics, it is but reasonable to suppose that a succession of dry seasons will considerably influence the flora of any locality. Heat and humidity, therefore, are intimately concerned in the mycologic vegetation of a country. Fries has noted in his essay the features to which we have alluded. "The fact," he says, "must not be lost sight of that some species of fungi which have formerly been common in certain localities may become, within our lifetime, more and more scarce, and even altogether cease to grow there. The cause of this, doubtless, is the occurrence of some change in the physical constitution of a locality, such as that resulting from the destruction of a forest, or from the drainage, by ditches and cuttings, of more or less extensive swamps, or from the cultivation of the soil--all of them circumstances which cause the destruction of the primitive fungaceous vegetation and the production of a new one. If we compare the fungal flora of America with that of European countries, we observe that the former equals, in its richness and the variety of its forms, that of the phanerogamous flora; it is probable, however, that, in the lapse of more or fewer years, this richness will decrease, in consequence of the extension of cultivation--as is illustrated, indeed, in what has already taken place in the more thickly peopled districts, as, for example, in the vicinity of New York."

Although heat and humidity influence all kinds of vegetation, yet heat seems to exert a less, and humidity a greater, influence on fungi than on other plants. It is chiefly during the cool moist autumnal weather that the fleshy fungi flourish most vigorously in our own country, and we observe their number to increase with the humidity of the season. Rain falls copiously in the United States, and this is one of the most fruitful countries known for the fleshy fungi. Hence it is a reasonable deduction that moisture is a condition favourable to the development of these plants. The Myxogastres, according to Dr. Henry Carter, are exceedingly abundant--in individuals, at least, if not in species--in Bombay, and this would lead to the conclusion that the members of this group are influenced as much by heat as humidity in their development, borne out by the more plentiful appearance of the species in this country in the warmer weather of summer.

In the essay to which we have alluded, Fries only attempts the recognition of two zones in his estimate of the distribution of fungi, and these are the temperate and tropical. The frigid zone produces no peculiar types, and is poor in the number of species, whilst no essential distinction can be drawn between the tropical and sub-tropical with our present limited information. Even these two zones must not be accepted too rigidly, since tropical forms will in some instances, and under favourable conditions, extend far upwards into the temperate zone.

"In any region whatever," writes Fries, "it is necessary, in the first instance, to draw a distinction between its open naked plains and its wooded tracts. In the level open country there is a more rapid evaporation of the moisture by the conjoined action of the sun and wind; whence it happens that such a region is more bare of fungi than one that is mountainous or covered by woods. On the other hand, plains possess several species peculiar to themselves; as, for example, Agaricus pediades, certain Tricholomata, and, above all, the family Coprini, of which they may be regarded as the special habitat. The species of this family augment in number, in any given country, in proportion to the extent and degree of its cultivation; for instance, they grow more luxuriantly in the province of Scania, in Sweden--a district farther distinguished above all others by its cultivation and fertility. In well-wooded countries moisture is retained a much longer time, and, as a result, the production of fungi is incomparably greater; and it is here desirable to make a distinction between the fungi growing in forests of resinous-wooded trees (Coniferæ) and those which inhabit woods of other trees, for these two descriptions of forests may be rightly regarded, as to their fungaceous growths, as two different regions. Beneath the shade of Coniferæ, fungi are earlier in their appearance; so much so, that it often happens they have attained their full development when their congeners in forests of non-resinous trees have scarcely commenced their growth. In woods of the latter sort, the fallen leaves, collected in thick layers, act as an obstacle to the soaking of moisture into the earth, and thereby retard the vegetation of fungi; on the other hand, such woods retain moisture longer. These conditions afford to several large and remarkable species the necessary time for development. The beech is characteristic of our own region, but, further north this tree gives place to the birch. Coniferous woods are, moreover, divisible into two regions--that of the pines and that of the firs. The latter is richer in species than the former, because, as is well known, fir-trees flourish in more fertile and moister soils. Whether, with respect to the South of Europe, other subdivisions into regions are required, we know not; still less are we able to decide on the like question in reference to the countries beyond Europe."

In very cold countries the higher fungi are rare, whilst in tropical countries they are most common at elevations which secure a temperate climate. In Java, Junghuhn found them most prolific at an elevation of 3,000 to 5,000 feet; and in India, Dr. Hooker remarked that they were most abundant at an elevation of 7,000 to 8,000 feet above the sea level.

For the higher fungi we must be indebted to the summary made by Fries, to which we have little to add.

The genus Agaricus occupies the first place, and surpasses, in the number of species, all the other generic groups known. It appears, from our present knowledge, that the Agarici have their geographic centre in the temperate zone, and especially in the colder portion of that zone. It is a curious circumstance that all the extra-European species of this genus Agaricus may be referred to various European subgenera.

In tropical countries it appears that the Agarici occupy only a secondary position in relation to other genera of fungi, such as Polyporus, Lenzites, etc. North America, on the other hand, is richer in species of Agaricus than Europe; for whilst the majority of typical forms are common to both continents, America further possesses many species peculiar to itself. In the temperate zone, so close is the analogy prevailing between the various countries in respect to the Agaricini, that from Sweden to Italy, and as well in England as North America, the same species are to be found. Of 500 Agaricini met with in St. Petersburg, there are only two or three which have not been discovered in Sweden; and again, of fifty species known in Greenland, there is not one that is not common in Sweden. The same remarks hold good in reference to the Agaricini of Siberia, Kamtschatka, the Ukraine, etc. The countries bordering upon the Mediterranean possess, however, several peculiar types; and Eastern and Western Europe present certain dissimilarities in their Agaric inhabitants. Several species, for example, of Armillaria and Tricholoma, which have been found in Russia, have been met with in Sweden only in Upland, that is, in the most eastern province; all the species which belong to the so-called abiegno-rupestres and pineto-montanæ regions of Sweden are wanting in England; and it is only in Scotland that the species of northern mountainous and pine-bearing regions are met with--a circumstance explicable from the similarity in physical features between Sweden and the northern portions of Great Britain.

The species of Coprinus appear to find suitable habitats in every quarter of the globe.

The Cortinariæ predominate in the north; they abound in Northern latitudes, especially on wooded hills; but the plains offer also some peculiar species which flourish during the rainy days of August and September. In less cold countries they are more scarce or entirely absent. The species of the genus Hygrophorus would at first seem to have a similar geographical distribution to those of the last group; but this is really not the case, for the same Hygrophori are to be found in nearly every country of Europe, and even the hottest countries (and those under the equator) are not destitute of representatives of this wide-spread genus.

The Lactarii, which are so abundant in the forests of Europe and North America, appear to grow more and more scarce towards both the south and north. The same may be stated in regard to Russula.

The genus Marasmius is dispersed throughout the globe, and everywhere presents numerous species. In inter-tropical countries they are still more abundant, and exhibit peculiarities in growth which probably might justify their collection into a distinct group.

The genera Lentinus and Lenzites are found in every region of the world; their principal centre, however, is in hot countries, where they attain a splendid development. On the contrary, towards the north they rapidly decrease in number.

The Polypori constitute a group which, unlike that of the Agarics, especially belongs to hot countries. The Boleti constitute the only exception to this rule, since they select the temperate and frigid zones for their special abode, and some of them at times find their way to the higher regions of the Alps. No one can describe the luxuriance of the torrid zone in Polypori and Trametes, genera of Hymenomycetes, which flourish beneath the shade of the virgin forests, where perpetual moisture and heat promote their vegetation and give rise to an infinite variety of forms. But though the genus Polyporus, which rivals Agaricus in the number of its species, inhabits, in preference, warm climates at large, it nevertheless exhibits species peculiar to each country. This arises from the circumstance that the Polypori, for the most part, live upon trees, and are dependent on this or that particular tree for a suitable habitat; and the tropical flora being prolific in trees of all kinds, a multitude of the most varied forms of these fungi is a necessary consequence. Hexagona, Favolus, and Laschia are common in inter-tropical countries, but they are either entirely absent or extremely rare in temperate climes.

When the majority of the species of a genus are of a fleshy consistence, it may generally be concluded that that genus belongs to a Northern region, even if it should have some representatives in lands which enjoy more sunshine. Thus the Hydna are the principal ornaments of Northern forests, where they attain so luxuriant a growth and beauty that every other country must yield the palm to Sweden in respect to them. In an allied genus, that of Irpex, the texture assumes a coriaceous consistence, and we find its species to be more especially inhabitants of warm climates.

Most of the genera of Auricularini are cosmopolitan, and the same is true of some species of Stereum, of Corticium, etc., which are met with in countries of the most different geographical position. In tropical countries, these genera of fungi assume the most curious and luxuriant forms. The single and not considerable genus Cyphella appears to be pretty uniformly distributed over the globe. The Clavariæi are equally universal in their diffusion, although more plentiful in the north; however, the genus Pterula possesses several exotic forms, though in Europe it has but two representative species. That beautiful genus of Hymenomycetes, Sparassis, occupies a similar place next the Clavariæi, and is peculiarly a production of the temperate zone and of the coniferous region.

The fungi which constitute the family of Tremellini prevail in Europe, Asia, and North America, and exhibit no marked differences amongst themselves, notwithstanding the distances of the several countries apart. It must, however, be stated that the Hirneolæ for the most part inhabit the tropics.

We come now to the Gasteromycetes--an interesting family, which exhibits several ramifications or particular series of developments. The most perfect Gasteromycetes almost exclusively belong to the warmer division of the temperate, and to the tropical zone, where their vegetation is the most luxuriant. Of late the catalogue of these fungi has been greatly enriched by the addition of numerous genera and species, proper to hot countries, previously unknown. Not uncommonly, the exotic floras differ from ours, not merely in respect of the species, but also of the genera of Gasteromycetes. It must, besides, be observed that this family is rich in well-defined genera, though very poor in distinct specific forms. Among the genera found in Europe, many are cosmopolitan.

The Phalloidei present themselves in the torrid zone under the most varied form and colouring, and comprise many genera rich in species. In Europe their number is very restricted. As we advance northward they decrease rapidly, so that the central districts of Sweden possess only a single species, the Phallus impudicus, and even this solitary representative of the family is very scarce. In Scania, the most southern province of Sweden, there is likewise but one genus and one species belonging to it, viz., the Mutinus caninus. Among other members of the Phalloidei, may be further mentioned the Lysurus of China, the Aseröe of Van Diemen's Land, and the Clathrus, one species of which, C. cancellatus, has a very wide geographical range; for instance, it is found in the south of Europe, in Germany, and in America; it occurs also in the south of England and the Isle of Wight; whereas the other species of this genus have a very limited distribution.

The Tuberacei are remarkable amongst the fungi in being all of them more or less hypogeous. They are natives of warm countries, and are distributed into numerous genera and species. The Tuberacei constitute in Northern latitudes a group of fungi very poor in specific forms. The few species of the Hymenogastres belonging to Sweden, with the exception of Hyperrhiza variegata and one example of the genus Octaviana, are confined to the southern provinces. The greater part of this group, like the Lycoperdacei, are met with in the temperate zone. Most examples of the genus Lycoperdon are cosmopolitan.

The Nidulariacei and the Trichodermacei appear to be scattered over the globe in a uniform manner, although their species are not everywhere similar. The same statement applies to the Myxogastres, which are common in Lapland, and appear to have their central point of distribution in the countries within the temperate zone. At the same time, they are not wanting in tropical regions, notwithstanding that the intensity of heat, by drying up the mucilage which serves as the medium for the development of their spores, is opposed to their development.

Of the Coniomycetes, the parasitic species, as the Cæomacei, the Pucciniei, and the Ustilagines, accompany their foster-plants into almost all regions where they are found; so that smut, rust, and mildew are as common on wheat and barley in the Himalayas and in New Zealand as in Europe and America. Ravenelia and Cronartium only occur in the warmer parts of the temperate zone, whilst Sartvellia is confined to Surinam. Species of Podisoma and Roestelia are as common in the United States as in Europe, and the latter appears also at the Cape and Ceylon. Wherever species of Sphæria occur there the Sphæronemei are found, but they do not appear, according to our present knowledge, to be so plentiful in tropical as in temperate countries. The Torulacei and its allies are widely diffused, and probably occur to a considerable extent in tropical countries.

Hyphomycetes are widely diffused; some species are peculiarly cosmopolitan, and all seem to be less influenced by climatic conditions than the more fleshy fungi. The Sepedoniei are represented by at least one species wherever Boletus is found. The Mucedines occur everywhere in temperate and tropical regions, Penicillium and Aspergillus flourishing as much in the latter as in the former. Botrytis and Peronospora are almost as widely diffused and as destructive in warmer as in temperate countries, and although from difficulty in preservation the moulds are seldom represented to any extent in collections, yet indications of their presence constantly occur in connection with other forms, to such an extent as to warrant the conclusion that they are far from uncommon. The Dematiei are probably equally as widely diffused. Species of Helminthosporium, Cladosporium, and Macrosporium seem to be as common in tropical as temperate climes. The distribution of these fungi is imperfectly known, except in Europe and North America, but their occurrence in Ceylon, Cuba, India, and Australasia indicated a cosmopolitan range. Cladosporium herbarum would seem to occur everywhere. The Stilbacei and Isariacei are not less widely diffused, although as yet apparently limited in species. Isaria occurs on insects in Brazil as in North America, and species of Stilbum and Isaria are by no means rare in Ceylon.

The Physomycetes have representatives in the tropics, species of Mucor occurring in Cuba, Brazil, and the southern states of North America, with the same and allied genera in Ceylon. Antennaria and Pisomyxa seem to reach their highest development in hot countries.

The Ascomycetes are represented everywhere, and although certain groups are more tropical than others, they are represented in all collections. The fleshy forms are most prolific in temperate countries, and only a few species of Peziza affect the tropics, yet in elevated districts of hot countries, such as the Himalayas of India, Peziza, Morchella, and Geoglossum are found. Two or three species of Morchella are found in Kashmir, and at least one or two in Java, where they are used as food. The genus Cyttaria is confined to the southern parts of South America and Tasmania. The United States equal if they do not exceed European states in the number of species of the Discomycetes. The Phacidiacei are not confined to temperate regions, but are more rare elsewhere. Cordierites and Acroseyphus (?) are tropical genera, the former extending upwards far into the temperate zone, as Hysterium and Rhytisma descend into the tropics. Amongst the Sphæriacei, Xylaria and Hypoxylon are well represented in the tropics, such species as Xylaria hypoxylon and Xylaria corniformis being widely diffused. In West Africa an American species of Hypoxylon is amongst the very few specimens that have ever reached us from the Congo, whilst H. concentricum and Ustulina vulgaris seem to be almost cosmopolitan. Torrubia and Nectria extend into the tropics, but are more plentiful in temperate and sub-tropical countries. Dothidea is well represented in the tropics, whilst of the species of Sphæria proper, only the more prominent have probably been secured by collectors; hence the Superficiales section is better represented than the Obtectæ, and the tropical representatives of foliicolous species are but few. Asterina, Micropeltis, and Pemphidium are more sub-tropical than temperate forms. The Perisporiacei are represented almost everywhere; although species of Erysiphe are confined to temperate regions, the genus Meliola occupies its place in warmer climes. Finally, the Tuberacei, which are subterranean in their habits, are limited in distribution, being confined to the temperate zone, never extending far into the cold, and but poorly represented out of Europe. One species of Mylitta occurs in Australia, another in China, and another in the Neilgherries of India; the genus Paurocotylis is found in New Zealand and Ceylon. It is said that a species of Tuber is found in Himalayan regions, but in the United States, as well as in Northern Europe, the Tuberacei are rare.