Word Finder - fungi

definition

Any member of the kingdom Fungi; a eukaryotic organism typically having chitin cell walls but no chlorophyll or plastids. Fungi may be unicellular or multicellular.

definition

A spongy, abnormal excrescence, such as excessive granulation tissue formed in a wound.

These two fungi usually grow in woods, but sometimes in hedges and in shady places in meadows, or even, as has been said, as invaders on mushroom-beds.

It is by many esteemed as the best of all the edible fungi found in Great Britain.

By far the greater number of spot-diseases are due to Fungi, as indicated by the numerous leaf-diseases described, but such is by no means always the case.

Many other fungi in addition to the fairy-ring champignon grow in circles, so that this habit must merely be taken with its other characters in cases of doubt.

Parasitic Fungi may be, as regards their direct action, purely locale.g.

The algal fungi, Phycomycetes, are obviously derived from the Green Algae, while the remaining Fungi, the Eumycetes, appear to have sprung from the same stock as the Rhodophyceae.

The pear is subject to several diseases caused by fungi.

The Nuclei of the Lower Plants.It is only in comparatively recent times that it has been possible to determine with any degree of certainty that the minute deeply stainable bodies described more especially by Schmitz (1879) in many Algae and Fungi could be regarded as true nuclei.

Other parasitic fungi of less economic importance occasionally do considerable damage.

This will help avoid inhalation of high levels of fungi.

Many edible fungi depend upon minute and often obscure botanical characters for their determination, and may readily be confounded with worthless or poisonous species; but that is not the case with the common mushroom, for, although several other species of Agaricus somewhat closely approach it in form and colour, yet the true mushroom, if sound and freshly gathered, may be distinguished from all other fungi with great ease.

The group has until recent years been regarded as comprising three classes distinguished by well-marked physiological featuresthe Algae (including the Seaweeds) which contain chlorophyll, the Fungi which have no chlorophyll and therefore lead a saprophytic or parasitic mode of life, and the Lichens which are composite organisms consisting of an alga and a fungus living together in a mutual parasitism (symbiosis); Bacteria were regarded as a section of Fungi.

The atmosphere is a cause of disease in the neighborhood of chemical works, large towns, volcanoes, &c., in so far as it carrie, acid gases and poisons to the leaves and roots; but it is usual tc associate with it the action of excessive humidity which brings about those tender watery and more or less etiolated condition, which favor parasitic Fungi, and diminish transpiration and therefore nutrition.

This fungi grows primarily in moist dark matter such as soil, feces and decaying plants or trees.

The preference exhibited by yeast cells for sugar molecules is shared by mould fungi and soluble enzymes in their fermentative actions.

Fungi under any circumstances form the least satisfactory portion of an herbarium.

In many of the Fungi the non-motile male cell or nucleus is carried by means of a fertilizing tube actually into the interior of the egg-cell, and is extruded through the apex in close proximity to the egg nucleus.

In Monoblepliaris, one of the lower Fungi, in some Algae, in the Vascular Cryptograms, in Cycads (Zamia and Cycas), and in Ginkgo, an isolated genus of Gymnosperms, the male cell is a motile spermatozoid with two or more cilia.

The union of the germ nuclei has now been observed in all the main groups of Angiosperms, Gymnosperms, Ferns, Mosses, Algae and Fungi, and presents a striking resemblance in all.

These changes may be brought about by external causes, such as the attacks of insects or of fungi, alterations in external conditions, &c., or by some unexplained internal disturbance of the morphological equilibrium.

In examining the tissues of fossil plants of that epoch nothing is more common than to meet with mycelial hyphae in and among the cells; in many cases the hyphae are septate, showing that the higher Fungi (Mycomycetes), as distinguished from the more algoid Phycomycetes, already existed.

In other lichens we should expect to find the ascogenous hyphae arising directly from the vegetative hyphae as in Humaria rutilans among the ordinary fungi, where the process is associated with the fusion of vegetative nuclei.

The spores are ejected from the apothecia and peri thecia as in the fungi by forcible ejacu lation from the asci.

The so-called Gasterolichens, Trichocoma and Emeri- cella, have been shown to be merely ascomycetous fungi.

They also differ very markedly from free living fungi in their chemical reactions.

Sloes and bird cherries should be removed from the neighbourhood of plum-trees, as the various disease-producing insects and fungi live also on these species.

Algae and fungi also were present, but there were no flowering plants.

While some moulds (Penicillium, Aspergillus) can utilize almost any organic food-materials, other fungi are more restricted in their choice - e.g.

It was formerly the custom to include with the Fungi the Schizomycetes or Bacteria, and the Myxomycetes or Mycetozoa; but the peculiar mode of growth and division, the cilia, spores and other peculiarities of the former, and the emission of naked amoeboid masses of protoplasm, which creep and fuse to streaming plasmodia, with special modes of nutrition and spore-formation of the latter, have led to their separation as groups of organisms independent of the true Fungi.

On the other hand, lichens, previously regarded as autonomous plants, are now known to be dual organisms - fungi symbiotic with algae.

The number of species in 1889 was estimated by Saccardo at about 32,000, but of these 8500 were so-called Fungi imperfecti - i.e.

When we remember that many parts of the world are practically unexplored as regards fungi, and that new species are constantly being discovered in the United States, Australia and northern Europe - the best explored of all - it is clear that no very accurate census of fungi can as yet be made, and no generalizations of value as to their geographical distribution are possible.

The existence of fossil fungi is undoubted, though very few of the identifications can be relied on as regards species or genera.

Appressoria are also formed by some parasitic fungi, as a minute flattening of the tip of a very short branch (Erysiphe), or the swollen end of any hypha which comes in contact with the surface of the host (Piptocephalis, Syncephalis), haustoria piercing in each case the cell-wall below.

Many fungi (Phallus, Agaricus, Fumago, &c.) when strongly growing put out ribbon-like or cylindrical cords, or sheet-like mycelial plates of numerous parallel hyphae, all growing together equally, and fusing by anastomoses, and in this way extend long distances in the soil, or over the surfaces of leaves, branches, &c. These mycelial strands may be white and tender, or the outer hyphae may be hard and black, and very often the resemblance of the subterranean forms to a root is so marked that they are termed rhizomorphs.

The various sclerotia, if kept moist, give rise to the fructifications of the fungi concerned, much as a potato tuber does to a potato plant, and in the same way the reserve materials are consumed.

In the more complex tissue-bodies of higher fungi, however, we find considerable differences in the various layers or strands of hyphae.

As regards its composition, the cell-wall of fungi exhibits variations of the same kind as those met with in higher plants.

The cells of fungi, in addition to protoplasm, nuclei and sap-vacuoles, like other vegetable cells, contain formed and amorphous bodies of various kinds.

Among the enzymes already extracted from fungi are invertases (yeasts, moulds, &c.), which split cane-sugar and other complex sugars with hydrolysis into simpler sugars such as dextrose and levulose; diastases, which convert starches into sugars (Aspergillus, &c.); cytases, which dissolve cellulose similarly (Botrytis, &c.); peptases, using the term as a general one for all enzymes which convert proteids into peptones and other bodies (Penicillium, &c.); lipases, which break up fatty oils (Empusa, Phycomyces, &c.); oxydases, which bring about the oxidations and changes of colour observed in Boletus, and zymase, extracted by Buchner from yeast, which brings about the conversion of sugar into alcohol and carbondioxide.

That such enzymes are formed in the protoplasm is evident from the behaviour of hyphae, which have been observed to pierce cell-membranes, the chitinous coats of insects, artificial collodion films and layers of wax, &c. That a fungus can secrete more than one enzyme, according to the materials its hyphae have to attack, has been shown by the extraction of diastase, inulase, trehalase, invertase, maltase, raffinase, malizitase, emulsin, trypsin and lipase from Aspergillus by Bourquelot, and similar events occur in other fungi.

The same fact is indicated by the wide range of organic substances which can be utilized by Penicillium and other moulds, and by the behaviour of parasitic fungi which destroy various cell-contents and tissues.

Many of the coloured pigments of fungi are fixed in the cell-walls or excreted to the outside (Peziza aeruginosa).

Matruchot has used them for staining the living protoplasm of other fungi by growing the two together.

Although many fungi have been regarded as devoid of nuclei, and all have not as yet been proved to contain them, the numerous investigations of recent years have revealed them in the cells of all forms thoroughly examined, and we are justified in concluding that the nucleus is as essential to the cell of a fungus as to that of other organisms. The hyphae of many contain numerous, even hundreds of nuclei (Phycomycetes); those of others have several (Aspergillus) in each segment, or only two (Exoascus) or one (Erysiphe) in each cell.

As with other plants, so in fungi the essential process of fertilization consists in the fusion of two nuclei, but owing to the absence of well-marked sexual organs from many fungi, a peculiar interest attaches to certain nuclear fusions in the vegetative cells or in young spores of many forms. Thus in Ustilagineae the chlamydospores, and in Uredineae the teleutospores, each contain two nuclei when young, which fuse as the spores mature.

Physiologically, any cell or group of cells separated off from a hypha or unicellular fungus, and capable of itself growing out - germinating - to reproduce the fungus, is a spore; but it is evident that so wide a definition does not exclude the ordinary vegetative cells of sprouting fungi, such as yeasts, or small sclerotium like cell-aggregates of forms like Coniothecium.

In practice these various kinds of spores of fungi receive further special names in the separate groups, and names, more over, which will appear, to those unacquainted with the history, to have been given without any consistency or regard to general principles; nevertheless, for ordi nary purposes these names are far more useful in most cases, owing to their descriptive character, than the proposed new names, which have been only partially accepted.

The recent work of the last twelve years has shown, however, that the two higher groups of fungi exhibit distinct sexuality, of either a normal or reduced type, and has also rendered very doubtful the view of the origin of these two groups from the Phycomycetes.

The real difficulty of classification of the fungi lies in the polyphyletic nature of the group. There is very little doubt that the primitive fungi have been derived by degradation from the lower algae.