Chapter 25

As to the cultivation of moulds and _Mucors_, one great difficulty has to be encountered in the presence or introduction of foreign spores to the matrix employed for their development. Bearing this in mind, extensive cultivations may be made, but the conditions must influence the decision upon the results. Rice paste has been used with advantage for sowing the spores of moulds, afterwards keeping them covered from external influences. In cultivation on rice paste of rare species, the experimenter is often perplexed by the more rapid growth of the common species of _Mucor_ and _Penicillium_. Mr. Berkeley succeeded in developing up to a certain point the fungus of the Madura Foot, but though perfect sporangia were produced, the further development was masked by the outgrowth of other species. In like manner, orange juice, cut surfaces of fruits, slices of potato tubers, etc., have been employed. Fresh, horse-dung, placed under a bell glass and kept in a humid atmosphere, will soon be covered with _Mucor_, and in like manner the growth of common moulds upon decayed fruit may be watched; but this can hardly be termed cultivation unless the spores of some individual species are sown. Different solutions have been proposed for the growth of such conditions as the cells which induce fermentation, to which yeast plants belong. A fly attacked by _Empusa muscæ_, if immersed in water, will develop one of the _Saprolegniæ_.

The _Uredines_ and other epiphyllous _Coniomycetes_ will readily germinate by placing the leaf which bears them on damp sand, or keeping them in a humid atmosphere. Messrs. Tulasne and De Bary have, in their numerous memoirs, detailed the methods adopted by them for different species, both for germination of the pseudospores and for impregnating healthy foster plants. The germination of the pseudospores of the species of _Podisoma_ may easily be induced, and secondary fruits obtained. The germination of the spores of _Tilletia_ is more difficult to accomplish, but this may be achieved. Mr. Berkeley found no difficulty, and had the stem impregnated as well as the germen. On the other hand, the pseudospores of _Cystopus_, when sown in water on a slip of glass, will soon produce the curious little zoospores in the manner already described.

The sporidia of the _Discomycetes_, and some of the _Sphæriacei_, germinate readily in a drop of water on a slip of glass, although not proceeding further than the protrusion of germ-tubes. A form of slide has been devised for growing purposes, in which the large covering glass is held in position, and one end of the slip being kept immersed in a vessel of water, capillary attraction keeps up the supply for an indefinite period, so that there is no fear of a check from the evaporation of the fluid. Even when saccharine solutions are employed this method may be adopted.

The special cultivation of the _Peronosporei_ occupied the attention of Professor De Bary for a long time, and his experiences are detailed in his memoir on that group,[O] but which are too long for quotation here, except his observations on the development of the threads of _Peronospora infestans_ on the cut surface of the tubers of diseased potatoes. When a diseased potato is cut and sheltered from dessication, the surface of the slice covers itself with the mycelium and conidiiferous branches of _Peronospora_, and it can easily be proved that these organs originate from the intercellulary tubes of the brown tissue. The mycelium that is developed upon these slices is ordinarily very vigorous; it often constitutes a cottony mass of a thickness of many millimetres, and it gives out conidiiferous branches, often partitioned, and larger and more branched than those observed on the leaves. The appearance of these fertile branches ordinarily takes place at the end of from twenty-four to forty-eight hours; sometimes, nevertheless, one must wait for many days. These phenomena are observed in all the diseased tubercles without exception, so long as they have not succumbed to putrefaction, which arrests the development of the parasite and kills it.

Young plants of the species liable to attack may be inoculated with the conidia of the species of _Peronospora_ usually developed on that particular host, in the same manner that young cruciferous plants, watered with an infusion of the spores of _Cystopus candidus_, will soon exhibit evidence of attack from the white rust.

It is to the cultivation and close investigation of the growth and metamorphoses of the minute fungi that we must look for the most important additions which have yet to be made to our knowledge of the life-history of these most complex and interesting organisms.

[A] Experiments were made at Belvoir, by Mr. Ingram, in the cultivation of several species of _Agaricini_, but without success, and a similar fate attended some spawn of a very superior kind from the Swan River, which was submitted to the late Mr. J. Henderson. No result was obtained at Chiswick, either from the cultivation of truffles or from the inoculation of grass-plots with excellent spawn. Mr. Disney's experiments at the Hyde, near Ingatestone, were made with dried truffles, and were not likely to succeed. The Viscomte Nôe succeeded in obtaining abundant truffles, in an enclosed portion of a wood fenced from wild boars, by watering the ground with an infusion of fresh specimens; but it is possible that as this took place in a truffle country, there might have been a crop without any manipulation. Similar trials, and it is said successfully, have been made with _Boletus edulis_. Specimens of prepared truffle-spawn were sent many years since to the "Gardener's Chronicle," but they proved useless, if indeed they really contained any reliable spawn.

[B] Robinson, "On Mushroom Culture," London, 1870. Cuthill, "On the Cultivation of the Mushroom," 1861. Abercrombie, "The Garden Mushroom; its Culture, &c." 1802.

[C] This has, however, not been confirmed, and is considered (how justly we cannot say) a "canard."

[D] This method is pursued with great success by Mr. Ingram, at Belvoir, and by Mr. Gilbert, at Burleigh.

[E] Cuthill, "Treatise on the Cultivation of the Mushroom," p. 9.

[F] Mr. Berkeley lately recommended, at one of the meetings of the Horticultural Society at South Kensington, that the railway arches should be utilized for the cultivation of mushrooms.

[G] Badham, "Esculent Funguses," 1st ed. p. 43.

[H] Broome, "On Truffle Culture," in "Journ. Hort. Soc." i. p. 15 (1866).

[I] No faith, however, is, in general, placed on these treatises, as they were merely conjectural.

[J] Dr. Bull has been very successful in developing the _Sclerotium_ of _Agaricus cirrhatus_.

[K] Currey, "On Development of _Sclerotium roseum_," in "Journ. Linn. Soc." vol. i. p. 148.

[L] Currey, in "Linn. Trans." xxiv. pl. 25, figs. 17, 26.

[M] Berkeley, "On Two Tuberiform Veg. Productions from Travancore," in "Trans. Linn. Soc." vol. xxiii. p. 91.

[N] Berkeley, "On a Peculiar Form of Mildew in Onions," "Journ. Hort. Soc." vol. iii p. 91.

[O] De Bary, "Ann. des Sci. Nat." 4th series, vol. xx.

XIII.

GEOGRAPHICAL DISTRIBUTION.

Unfortunately no complete or satisfactory account can be given of the geographical distribution of fungi. The younger Fries,[A] with all the facilities at his disposal which the lengthened experience and large collections of his father afforded, could only give a very imperfect outline, and now we can add very little to what he has given. The cause of this difficulty lies in the fact that the Mycologic Flora of so large a portion of the world remains unexplored, not only in remote regions, but even in civilized countries where the Phanerogamic Flora is well known. Europe, England, Scotland, and Wales are as well explored as any other country, but Ireland is comparatively unknown, no complete collection having ever been made, or any at least published. Scandinavia has also been well examined, and the northern portions of France, with Belgium, some parts of Germany and Austria, in Russia the neighbourhood of St. Petersburg, and parts of Italy and Switzerland. Turkey in Europe, nearly all Russia, Spain, and Portugal are almost unknown. As to North America, considerable advances have been made since Schweinitz by Messrs. Curtis and Ravenel, but their collections in Carolina cannot be supposed to represent the whole of the United States; the small collections made in Texas, Mexico, etc., only serve to show the richness of the country, not yet half exhausted. It is to be hoped that the young race of botanists in the United States will apply themselves to the task of investigating the Mycologic Flora of this rich and fertile region. In Central America very small and incomplete collections have as yet been made, and the same may be said of South America and Canada. Of the whole extent of the New World, only the Carolina States of North America can really be said to be satisfactorily known. Asia is still less known, the whole of our vast Indian Empire being represented by the collections made by Dr. Hooker in the Sikkim Himalayas, and a few isolated specimens from other parts. Ceylon has recently been removed from the category of the unknown by the publication of its Mycologic Flora.[B] All that is known of Java is supplied by the researches of Junghuhn; whilst all the rest is completely unknown, including China, Japan, Siam, the Malayan Peninsula, Burmah, and the whole of the countries in the north and west of India. A little is known of the Philippines, and the Indian Archipelago, but this knowledge is too fragmentary to be of much service. In Africa no part has been properly explored, with the exception of Algeria, although something is known of the Cape of Good Hope and Natal. The Australasian Islands are better represented in the Floras published of those regions. Cuba and the West Indies generally are moderately well known from the collections of Mr. C. Wright, which have been recorded in the journal of the Linnæan Society, and in the same journal Mr. Berkeley has described many Australian species.

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."[C]

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.