1934/01/01 by J. B. Cleland · 1 voice · 5 citations
Agricultural and Biological Sciences · Biochemistry, Genetics and Molecular Biology · #Lichen and fungal ecology #Mycorrhizal Fungi and Plant Interactions #Plant Pathogens and Fungal Diseases
paper · doi:10.5962/bhl.title.112109
openalex publication_date 1934/01/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/02
The fungi comprise a very large section of the vegetable kingdom, Being destitute of chlorophyll, anil thus differing from the green plants, they are unable to utilise the < sir bon present in the atmosphere as carbon dioxide.They are thus compelled to live a saprophytic, or in some cases a parasitic, existence, deriving their supplies of carbon and also other necessary substances from organic material which has been formed directly or indirectly from chlorophyllcontaining plants.In the course of obtaining their food from these various sources, they disintegrate the material and break down the complex chemical compounds composing it into substances of simpler nature, preparatory to building these up again into other forms as part of their own substance.Even the parasitic members obtain their nourishment in the same way.Mechanical as well as biochemical factors participate in the disintegration.We sometimes see bracket fungi growing on telegraph posts, or the rails of a fence, or on the prostrate trunk of a forest tree.These are the fruiting bodies of fungi wliose mycelial threads permeate the adjacent wood where their presence can be recognised by the altered appearance and texture.The affected portion is easily broken down and readily crumbles.Part of the air-spaces that were present in the dead wood have become tilled by the fungous threads, so that the wood now smoulders on the fire instead of burning freely.With access of moisture, the mycelial threads become turgid and so tend to rend asunder the wood fibres in their neighbourhood, and in addition ferments are secreted by the growing mycelium which lead to chemical disintegration as well.When in the forest the trunk of a tree falls to the ground and wet weather supervenes, fungi of various kinds and bacteria invade the dead material, gradually permeate it, and in the ways mentioned lead eventually to its complete disintegration, being aided in the process by other lowly forms of life, and by insects and related animals.With warmth, the process is hurried up, if sufficient moisture be present so as to give a. humid atmosphere; with cold it is retarded, and in the relative absence of moisture it is arrested or nearly so.In. the arid interior of Australia, unless attacked by termites, the destruction of timber is exceedingly slow, whilst in a t ropical jungle a great tree that has fallen may disappear entirely in a surprisingly short time.Were it not for this beneficent disin- tegration by fungi and bacteria, the forest floor would soon become deeply littered with fallen boughs and leaves and a rich humus would fail to develop.Seedling plants would not find room to grow, and in the course of time the forest itself would necessarily cease to exist.Fungi, aided by bacteria, are then the great scavengers of the forest and of effete plant material as a whole, just as bacteria aided by insects are, under natural conditions, the chief means of removing animal carcases.The forest tree is like Imperial Caesar, and the "clay'' to which each is turned serves an ever-useful purpose and is again built up to form forest-trees and Caesars of a younger generation.It is not the purpose of this Handbook to deal with the great group of fungi as a whole.This would be a stupendous task, even dealing with the South Australian members alone.There are so many branches, and the work in each is so specialised, that the various divisions would require to be dealt with by separate workers.It is advisable, however, to indicate briefly what these different divisions are, so that we may appreciate more clearly the relationship borne by our special subject to its allies in mycology.The bacteria are closely related to the fungi and pass by almost imperceptible gradations from unques- tioned bacteria to quite obvious fungi.To the bacteriologist dealing with human, animal, or plant diseases, or with the bacteriology of the soil, or the maturing of tobaceo, or the making of butter, or the tanning of leather, or even the manufacture of white lead, we leave the bacteria.To one of his tribe wo leave also the study of such true fungus diseases of man as ringworm and thrush, as well as the yeasts, also true fungi, that make our bread rise or brew our beer.This Handbook will not deal either with the many kinds of moulds that grow on damp bread, that cover our boots in the tropics, or cause patches and decay on tarpaulins, or sometimes disfigure the carcases of meat in cold storage.These fungal organisms and their allies are many, most are minute and require microscopic study to appreciate them at all, their structure as fungi JO THE LARGER FUNGI is relatively simple, find they form no large and obvious fruiting bodies.More- over, we will not consider the microscopic, fungi that play such a part in injuring plants of economic importance to man.This group falls to the lot of the plant pathologist.The majority of these fungi are microscopic in themselves, though the reactions in the host-plant's tissues to which they give rise may be quite large and striking in appearance.The rusty galls on many of our acacias due to species of Vromycladium are an example in point.In some cases, indeed, the fungus itself may form a body obvious to the naked eye and of a definite shape, as is the case with the sclerotium of ergot found on one at least of our native grasses.However, as a rule there does not occur amongst these plant pests any fungous forms that suggest at all closely a. "toadstool," a mushroom, a bracket fungus, a eoral-or jelly-fungus, or a puffball.The majority of the diseases of plants, shown by wilting, spots on leaves, pustules, die backs, warty or distoi'ted growths and galls, when not due to insects or mites, are caused by fungi not closely related to the larger forms with which we are concerned.Occasionally such a disease, as for instance silver-leaf of plums, is due to the mycelium of one of these huger forms, though the fruiting of the fungus is rarely seen.However, such fungi as the rusts, though more or less microscopic, are not so distantly related to the toadstools as one might think.Moreover, we find that many of the fungi studied by the plant pathologist have their spores contained in special sacs called asei and these correspond with similar structures found in some large fleshy, and in some cases edible, fungi (such as MorcheVa) with which we shall deal.The fungi which live in intimate association with the roots of epiphytic orchids in tropical forests also do not come within the purview of tills Handbook.These fungi, living thus in symbiosis with the cells of these higher plants, are probably of material service lo the orchitis and would seem to lie essential for the development of their seeds.'The lichens constitute a curious class of plants inasmuch as each species is of composite origin, being the result of the intimate living together of a species of alga with a fungus species, the result being a structure entirely different in appearance from what would be seen were tho alga and the fungus each loading an independent existence.The lichens also arc outside our scope.With what then do we propose to deal?It is with a large group that in the fruiting condition exhibit obvious fleshy, leathery, woody, or jelly-like structures of a form and coloring peculiar to each particular species.Nearly all these forms are.classifiable under one division of the fungi known ns the Basidiomycetes, tho structure of which indicates that the plants concerned are amongst the most highly developed or complex of the fungi taken as a whole.In addition, we shall include also a few genera that show somewhat similar conspicuous more or less fleshy fruiting bodies, but which have their spores contained in sacs (asei), each sac possessing eight spores.This latter great division of the fungi is, in consequence, known as the Axcomyivtrx, and it is to be noted, as already stated, that some of the microscopic species of this division play a prominent part in the causation of plant diseases.We will not deal with these small forms or with a number of more or less saucer-shaped species amongst the Dtieomyectefi, which also have their spores in asei.These latter, varying in size from less than a threepenny piece to that of I m I f a crown or more, might quite well be included in out category, but no thorough attempt has as yet been made to work out the South Australian species.From the point of view of this Handbook, then, the "larger fungi ' 1 embrace all the BaMdiomyceles, even though some may be not much larger than a pin's head, together with a few of the most highly developed Ai<coniycetes that have prominent fleslxv fruiting bodies.As already stated, the Ascomyaetes are characterised by having the spores-or at least certain spores-contained at one time within definite little sacs.In the Basbdiomycetes, the spores are not developed in sacs, but are borne at the end of certain fungous hyphae, known as basidia, usually projecting from tho basidium on tne ends of delicate processes known as sterigmata.Each basidium usually support's four spores.The gills of a common mushroom possess numerous basidia with their free ends projecting from amongst the other hyphae, and on each basidium will be seen four sterigmata capped each with a spore.In this way the spores are raised from the surface on which they have developed so that when mature they can fall free from the gills and bo distributed around by currents of air.OF SOUTH AUSTRALIA.11 When a fungus spore finds a suitable medium in which to grow and begins to develop, it becomes transformed into a mycelial or fungous thread, both the spore and the thread being of microscopic size.This, as nourishment is absorbed, becomes longer and longer, transverse septa appear and branching takes place.The food supply becomes permeated by these strands.For days or weeks, or perhaps for years, the young fungus plant continues growing in this way when conditions, such as warmth and moisture, are favorable.Eventually a large portion of the food supply may in the end be converted into the fungous mycelium which may form a considerable mass of tissue, though not' necessarily a compact mass.During this active growth surplus material is stored up to be made use of, when the favourable time comes, for the rapid production of a definite fruiting structure in or on which multitudes of fresh spores will be formed.To take the common mushroom as an example, for many months the fungus plant labours at producing an abundant "spawn," in which is stored up material that can be rapidly transferred to produce the mushrooms them- selves.The spawn may live for several or many years, annually under suitable weather conditions producing a crop of mushrooms.These, though they may "come up in a night," do not really represent the result of a single night's work on the part of the fungus plant.The materials of which the mushroom is composed have taken a long time to elaborate.They have been stored up ready to be rapidly transferred to those points where, on the mass of fungous hyphae.the buds of the future mushrooms have been laid down.When the auspicious time comes, the transfer is rapidly made and in a single night, or at least in a short space of time, the mushroom itself emerges from the ground, in the words of Milton rising "like an exhalation," raises itself aloft, expands its cap and exposes its gills.We sometimes hear of a house being built in a day-more•correctly speaking we should say erected in a day.Much labour over many days has been spent in making the doors and fashioning the rafters and collecting the materials.The mushroom may be erected in a day, but the materials used in building it up have required weeks of constant incessant toil unseen, it is with these finished products, the fruiting bodies of the fungi concerned, that this Handbook deals.The more or less hidden mycelial strands of the various kinds of the higher fungi differ not so very much from each other, and are rarely compacted into definite masses or possess any special architecture.With the fruiting bodies, however, it is different, and by the arrangements of the parts, the colours, sizes, and shapes of the structures, the characteristics of the spores and other features, the various species can be readily recognised and described and their relationships with each other ascertained or con jectured.Though individual variations may lie considerable, the factors in common render the recognition of species possible to the mycologist who takes the pains to ascertain and define them.OF SOUTH AUSTRALIA.]3The spores of many of the puff-balls are spherical in shape and in the neighbourhood of 1/5,000 of an inch in diameter.Some are perfectly smooth, others rough.It sometimes happens that smooth spherical bodies of about this size are required for some purpose and such fungi suggest a source that may serve this end.Such small bodies offer much resistance to the downward pull of gravity, and consequently fall relatively slowly.Bui lor has shown that the spores, usually elliptical, of some agarics resembling the common mushroom fall about an inch a minute in a perfectly still atmosphere.Any little disturbances in the air, such as convection currents, blow the spores about in all directions, so that in the air of an ordinary room spores may remain suspended probably for hours, and some, instead of falling to the floor, may be found to have settled cm pictures or the ventilators near the ceiling.During the great influenza epidemic it was desired to know to what extent very minute dry particles might, be inhaled into the lungs, particles represented by droplets of saliva or sputum coughed into his surroundings by a patient suffering from the pneumonic form of influenza.Such particles, containing perhaps the living virus of the disease, would soon lose their moisture and, being very small, would like tobacco smoke be wafted hither and thither by currents of air.Though the spores of puff-balls were many times larger than these minute dried droplets of influenza spray, the spores being easily recognisable were chosen to ascertain with wliat rapidity minute particles could reach the deepest recesses in the lungs, the little terminal spaces or alveoli where the work of oxygenating the blood is carried out.Tt is held by many that the air in the utmost recesses is changed but slowly, and consequently small particles are not likely to reach them by inhalation, becoming glued to the mucus on the narrow passages leading to them.A monkey had a puffball pinched in front of its nose and was killed within a minute of this procedure.Even in this short space of time, a few spores had reached the alveoli where they were microscopically recognised.The spores of mushrooms have served detective purposes for public health ends.Some years ago in Sydney, burnt almonds were exposed for sale in a shop window in which mushrooms were also displayed.Specks on the sweets were believed to be due to the excreta of cockroaches, which abounded.Mushroom spores were recognised in the specks by their colour, shape, and size, and were also found in the alimentary canal of the cockroaches.In consequence of this undesirably deterioration of the food, the burnt almonds were seized and destroyed, even though their consumption would not' have been likely to injure health, unless these same cockroaches had had access also, as they might have had, to other definitely deleterious materials.The size, shape,