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mycelium

mycelium

mycelium Sentence Examples

  • In France mushroom-growers do not use the compact blocks or bricks of spawn so familiar in England, but much smaller flakes or "leaves" of dry dung in which the spawn or mycelium can be seen to exist.

  • The common mushroom (Agaricus campestris) is propagated by spores, the fine black dust seen to be thrown off when a mature specimen is laid on white paper or a white dish; these give rise to what is known as the "spawn" or mycelium, which consists of whitish threads permeating dried dung or similar substances, and which, when planted in a proper medium, runs through the mass, and eventually develops the fructification known as the mushroom.

  • This spawn may be obtained from old pastures, or decayed mushroom beds, and is purchased from nurserymen in the form of bricks charged with the mycelium, and technically known as mushroom spawn.

  • A characteristic feature of the fungal vegetative plantbody (mycelium) is its formation from independent coenocytic tubes or cell-threads.

  • This is especially the case in the lichens (symbiotic organisms composed of a fungal mycelium in association with algal cells), which are usually exposed to very severe fluctuations in external conditions.

  • The formation of a massive body naturally involves the localization of the absorptive region, and the function of absorption (which in the simpler forms is carried out by the whole of the vegetative part of the mycelium penetrating a solid or immersed in a liquid substratum) is subserved by the outgrowth of the hyphae of the surface-layer of that region into rhizoids, which, like those of the Algae living on soil, resemble the root-hairs of the higher plants.

  • Some make their way through the cells of the outer part of the cortex towards the root-tip, and form a mycelium or feltwork of hyphae, which generally occupies two or three layers of cells.

  • This wood is in great part already dead substance, but the mycelium gradually invades the vessels occupied with the transmission of water up the trunk, cuts off the current, and so kills the tree; in other cases such Fungi attack the roots, and so induce rot and starvation of oxygen, resulting in fouling.

  • The extraordinary malformations known as Witches Brooms, caused by the repeated branching and tufting of twigs in which the mycelium of Exoascus (on birch) or Aecidium (on silver fir) are living, may be borne in considerable ntimbers for years without any very extensive apparent injury to the tree.

  • White or grey spots may be due to Peronospora, Erysiphe, Cystopus, Entyloma and other Fungi, the mycelium of which will be detected in the discoloured area; or they may be scale insects, or the results of punctures by Red-spider, &c. Yellow spots, and especially bright orange spots, commonly indicate Rust Fungi or other Uredineae; but Phyllosticta, Exoascus, Clasterosporium, Synchytrium, &c., also induce similar symptoms. Certain Aphides, Red-spider, Phylloxera and other insects also betray their presence by such spots.

  • The fungus mycelium grows between the cuticle and the epidermis, the former being ultimately ruptured by numerous short branches bearing spores (conidia) by means of which the disease is spread.

  • In " Root rot," as the name implies, the roots are attacked, the fungus being a species of Ozonium, which envelops the roots in a white covering of mould or mycelium.

  • Portion of the mycelium of the fungus bearing spores (conidia), s, on erect branches, X250.

  • The disease is characterized by the appearance of a mycelium forming white or greyish-white patches on the young leaves; this spreads quickly and attacks the older leaves and branches, and ultimately reaches the grapes.

  • The disease spreads by the mycelium growing ever the epidermis of the plant.

  • A and B, mycelium (m), the mix t ure over the affe c ted with haustoria (h).

  • The mycelium spreads through the green parts of the plant, attacking the leaves, twigs and unripe grapes.

  • The mycelium of Sphaceloma grows just beneath the cuticle of the vine, through which it soon bursts, giving rise to a number of minute hyphae, which bear conidia.

  • Mycelium of the fungus attacking root of vine (reduced).

  • The hyphae of the mycelium of this fungus are septate, with numerous short branches.

  • 6), which forms subterranean strings of mycelium - so-called rhizomorphs.

  • The wood is nearly white, or of a yellowish tint, but sometimes exhibits blackish markings due to the mycelium of a fungus.

  • The mycelium produced from the spores dropped by the fungus or from the "spawn" in the soil, radiates outwards, and each year's successive crop of fungi rises from the new growth round the circle.

  • This prevents infection from outside and also destroys any spores or fungus mycelium that may have been packed away along with the bulbs.

  • By the fusion of the hyphae in the middle of the mycelium a pseudo-parenchymatous cortical layer has begun to form.

  • It any state most plants feed greedily upon it, and when pure or free from decaying wood or sticks it is a very safe ingredient in composts; but it is so liable to generate fungus, and the mycelium or spawn of certain fungi is so injurious to the roots of trees, attacking them if at all sickly or weakened by drought, that many cultivators prefer not' to mix leaf-mould with the soil used for permanent plants, as peaches or choice ornamental trees.

  • A widespread disease known as pocket-plums or bladderplums is due to an ascomycetous fungus, Exoascus pruni, the mycelium of which lives parasitically in the tissues of the host plant, passes into the ovary of the flower and causes the characteristic malformation of the fruit which becomes a deformed, sometimes curved or flattened, wrinkled dry structure, with a hollow occupying the place of the stone; the bladder plums are yellow at first, subsequently dingy red.

  • fungus, a mushroom), the botanical name covering in the broad sense all the lower cellular Cryptogams devoid of chlorophyll, which arise from spores, and the thallus of which is either unicellular or composed of branched or unbranched tubes or cell-filaments (hyphae) with apical growth, or of more or less complex wefted sheets or tissue-like masses of such (mycelium).

  • Mycelium with haustoria (h); 2, Erysiphe; A and B, mycelium (m), with haustoria (h).

  • In Arthrobotrys side-branches of the mycelium sling themselves around the host (Tylenchus) much as tendrils round a support.

  • The sporophore is obsolete when the spore-bearing hyphae are not sharply distinct from the mycelium, simple when the constituent hyphae are isolated, and compound when the latter are conjoined.

  • Much more complicated are the processes in a large series of "fructifications," where the mycelium first develops a densely packed mass of hyphae, all alike, in which labyrinths of cavities subsequently form by separation of hyphae in the previously homogeneous mass, and the hymenium covers the walls of these cavities and passages as with a lining layer.

  • Mycelium usually well developed, but sometimes poor or absent.

  • Mycelium present, antheridia with antherozoids, oogonium with single oosphere: Monoblepharidaceae.

  • Mycelium present; antheridia but no antherozoids; oogonia with one or more oospheres: Peronosporaceae, Saprolegniaceae.

  • Mycelium poorly developed or absent; oogonia and antheridia (without antherozoids) known in some cases; zoospores common: Chytridiaceae.

  • Mycelium well developed; sexual reproduction by zygospores; asexual reproduction by sporangia and conidia.

  • Life-history always very simple, no wellmarked alternation of generations; basidium borne directly on the mycelium.

  • Klebs has shown that the development of zoosporangia or of oogonia and pollinodia respectively in Saprolegnia is dependent on the external conditions; so long as a continued stream of suitable food-material is ensured the mycelium grows on without forming reproductive organs, but directly the supplies of nitrogenous and carbonaceous food fall below a certain degree of concentration sporangia are developed.

  • Those parts nearest the fly and best supplied develop barren hyphae only; in a zone at the periphery, where the products of putrefaction dissolved in the water form a dilute but easily accessible supply, the zoosporangia are developed in abundance; oogonia, however, are only formed in the depths of this radiating mycelium, where the supplies of available food materials are least abundant.

  • These parasitic and minute, chiefly aquatic, forms may be looked upon as degenerate Oomycetes, since a sexual process and feeble unicellular mycelium occur in some; or they may be regarded as series of primitive forms leading up to higher members.

  • In the first group zygospores can arise by the union of branches from the same mycelium and so can be produced by the growth from a single spore; this group includes Spordinia grandis, Spinellus fusiger, some species of Mucor, &c. The majority of forms, however, fall into the heterothallic group, in which the association of branches from two mycelia different in I nature is necessary for the 2, formation of zygospores.

  • The yeast-conidia, which bud off from the conidia or their resulting mycelium when sown in nutrient solutions, are developed in successive crops by budding exactly as in the yeast plant, but they cannot ferment sugar solutions.

  • mycelium is very much reduced in extent.

  • The asci are borne directly on the mycelium and are therefore fully exposed, being devoid from the beginning of any investment.

  • - The other divisions of the Ascomycetes may be distinguished as Carpoascomycetes because they do not bear the asci free on the mycelium but enclosed in definite fruit bodies or ascocarps.

  • m, Filaments of the mycelium cut transversely.

  • They form a superficial mycelium on the surface of the plant, the hyphae not usually penetrating the tissues but merely sending haustoria into the epidermal cells.

  • Only in rare cases is the mycelium intercellular.

  • (After De Bary.) A, Small portion of mycelium D, The perithecium.

  • (After Janczewski.) m, Mycelium.

  • The simpler forms bear the perithecia directly on the mycelium, but the more highly developed forms often bear them on a special mycelial development - the stroma, which is often of large size and special shape and colour, and of dense consistence.

  • When the sporidia infect a plant the mycelium so produced gives origin to aecidiospores and spermatia; the aecidiospores on infection produce a mycelium which bears uredospores and later teleutospores.

  • This is the lifehistory of the most complicated forms, of the so-called eu forms. In the opsis forms the uredospores are absent, the mycelium from the aecidiospores producing directly the teleutospores.

  • In brachy and hemi the aecidiospores are absent, the mycelium from the sporidia giving origin directly to the uredospores; the former possess spermatia, in the latter they are absent.

  • In lepto and micro forms both aecidiospores and uredospores are absent, the sporidia producing a mycelium which gives rise directly to teleutospores; in the lepto forms the teleutospores can germinate directly, in the micro forms only after a period of rest.

  • In the hemi, brachy, micro and lepto forms, which possess no aecidium, we find that the association takes place at various points in the ordinary mycelium but always A, Portion of a young aecidium.

  • Whether B, Formation of the first sporethe association of nuclei in the mother-cell (sm), from the ordinary mycelium takes place basal cell (a) of one of the by the migration of a nucleus rows of spores.

  • There is also a further reduction in that the basidium is not derived from a teleutospore but is borne directly on the mycelium.

  • mycelium ircdospores otachY' ar Mycelium aecidi'spores teleutospores (young) - mycelium SporoNtyte with conjugate nuclei GametohyEe with single nuclei teleutospores ?(mature) 8a ?; sporida ?m celium erm $ fertile cells Y sp (abortaitviae) (of aecidium) fertilized cells (of aecidium) and bears the basidiospores.

  • Exobasidium) the basidia are borne directly on the ordinary mycelium, but in the majority of cases the basidia are found developed in layers (hymenium) on special sporophores of characteristic form in the various groups.

  • In these sporophores (such as the well-known toadstools and mushrooms where the ordinary vegetative mycelium is underground) we have structures specially developed for bearing the basidiospores and protecting them from rain, &c., and for the distribution of the spores - see earlier part of article on distribution of spores (figs.

  • The underground mycelium in many cases spreads wider and wider each year, often in a circular manner, and the sporophores springing from it appear in the form of a ring - the so called fairy rings.

  • Nectria, Dasyscypha, &c.), or the enfeeblement of the tissues of the host, or invigoration of the fungus, the mycelium of which then becomes strong enough to overcome the host's resistance (Botrytis).

  • Such obligate parasites may be epiphytic (Erysipheae), the mycelium remaining on the outside and at most merely sending haustoria into the epidermal cells, or endophytic (Uredineae, Ustilagineae, &c.), when the mycelium is entirely inside the organs of the host.

  • An epiphytic fungus is not necessarily a parasite, however, as many saprophytes (moulds, &c.) germinate and develop a loose mycelium on living leaves, but only enter and destroy the tissues after the leaf has fallen; in some cases, however, these saprophytic epiphytes can do harm by intercepting light and air from the leaf (Fumago, &c.), and such cases make it difficult to draw the line between saprophytism and parasitism.

  • Endophytic parasites may be intracellular, when the fungus or its mycelium plunges into the cells and destroys their contents directly (Olpidium, Lagenidium, Sclerotinia, &c.), but they are far more frequently intercellular, at any rate while young, the mycelium growing in the lacunae between the cells (Peronospora, Uredineae) into which it may send short (Cystopus), or long and branched (Peronospora Calotheca) haustoria, or it extends in the middle lamella (Ustilago), or even in the solid substance of the cell-wall (Botrytis).

  • Similar gradations are observed in the direct effect of the parasite on the host, which may be local (Hemileia) when the mycelium never extends far from the point of infection, or general (Phytophthora) when it runs throughout the plant.

  • Trametes radiciperda attacks the roots and penetrates to the stem, causing rotting of the wood; the disease is difficult to eradicate, as the mycelium of the fungus travels from root to root in the soil.

  • These zoospores escape and swim about in any film of moisture, and on going to rest take a spherical form, germinate and produce threads of mycelium as at K.

  • The spores of the fungus pass the winter in the soil and the delicate mycelium attacks the young shoots in the summer.

  • The first signs of this fungus is the appearance of small white tufts of mycelium bursting through the skin of the tuber, the spores of the fungus being carried at the tips of the threads forming these tufts.

  • The ear loses its starch, and ceases to grow, and its ovaries become penetrated with the white spongy tissue of the mycelium of the fungus which towards the end of the season forms the sclerotium, in which state the fungus lies dormant through the winter.

  • The fine thread-like filaments composing the mycelium of the fungus are embedded in the tissue underneath and around the uredo-sorus, and draw from the host the nourishment required.

  • appressed, white mycelium were observed.

  • On PDA, the fungus quickly formed a dense white mycelium, which later became fluffy.

  • fungal mycelium evident on the sample at all.

  • Molds are composed of numerous, microscopic, branching hyphae known collectively as a mycelium.

  • It has a mycelium of narrow, branched and septate hyphae.

  • mushroom mycelium can commence.

  • mycelium of both species and Marasmius was potentially the better competitor.

  • In culture, it produced a pinkish-white mycelium with black, slimy conidial masses protruding from the surface.

  • Each fungus will have vast numbers of these hyphae, all intertwining to make up a tangled web called the mycelium.

  • On PDA, the fungus quickly formed a dense white mycelium, which later became fluffy.

  • Grows to form a fungus-like, branching mycelium with aerial hyphae bearing conidia.

  • In fact, there was no fungal mycelium evident on the sample at all.

  • Much of their life cycle is spent as vegetative mycelium, exploiting complex substrates.

  • Colonies on carrot agar (CA; Brasier, 1967) were slightly stellate with appressed to low tufted aerial mycelium (Fig.

  • mycelium growth of the fungi.

  • mycelium plugs were put on the hypocotyl, which was previously wounded with a sterile scalpel.

  • By using the dowels to inoculate cut logs or stumps, mushroom mycelium can be encouraged to grow throughout or colonize the wood.

  • Figure 1 shows the typical cobweb growth of a mold mycelium from the edge to the center of a glass surface.

  • As he lay there holding her corpse he realized that even a doctor mycelium could not have saved her.

  • Mold: Any superficial growth of a fungus mycelium.

  • mycelium epiphytic mycelia and conidia were present on leaves; forming thin, irregular colonies on either sides of leaves (Fig.

  • sporangium a hyaline mycelium bearing lemon-shaped sporangia which released motile zoospores after chilling in water, consistent with P. infestans.

  • As the mass grows it forms compact tufts that are collectively called a mycelium.

  • vegetative mycelium, exploiting complex substrates.

  • wind-borne asexual spores and the dormant phase is as mycelium in dead leaf matter during frosty or dry summer conditions.

  • In some of the true Ascomycetes, such as Penicillium glaucum, the conidia if grown in saccharine solutions, which they have the power of fermenting, develop single cell yeast-like forms, and do not - at any rate for a time - produce again the characteristic branching mycelium.

  • The spores on germination make a white felted mat, more or less dense, of mycelium; this, when compacted with dry, half-decomposed dung, is the mushroom spawn of gardeners.

  • In France mushroom-growers do not use the compact blocks or bricks of spawn so familiar in England, but much smaller flakes or "leaves" of dry dung in which the spawn or mycelium can be seen to exist.

  • The common mushroom (Agaricus campestris) is propagated by spores, the fine black dust seen to be thrown off when a mature specimen is laid on white paper or a white dish; these give rise to what is known as the "spawn" or mycelium, which consists of whitish threads permeating dried dung or similar substances, and which, when planted in a proper medium, runs through the mass, and eventually develops the fructification known as the mushroom.

  • This spawn may be obtained from old pastures, or decayed mushroom beds, and is purchased from nurserymen in the form of bricks charged with the mycelium, and technically known as mushroom spawn.

  • A characteristic feature of the fungal vegetative plantbody (mycelium) is its formation from independent coenocytic tubes or cell-threads.

  • This is especially the case in the lichens (symbiotic organisms composed of a fungal mycelium in association with algal cells), which are usually exposed to very severe fluctuations in external conditions.

  • The formation of a massive body naturally involves the localization of the absorptive region, and the function of absorption (which in the simpler forms is carried out by the whole of the vegetative part of the mycelium penetrating a solid or immersed in a liquid substratum) is subserved by the outgrowth of the hyphae of the surface-layer of that region into rhizoids, which, like those of the Algae living on soil, resemble the root-hairs of the higher plants.

  • The roots of many of the latter, while growing freely in the soil are found to be surrounded with a dense feltwork of fungal mycelium, which sometimes forms a mass of considerable size.

  • Some make their way through the cells of the outer part of the cortex towards the root-tip, and form a mycelium or feltwork of hyphae, which generally occupies two or three layers of cells.

  • This wood is in great part already dead substance, but the mycelium gradually invades the vessels occupied with the transmission of water up the trunk, cuts off the current, and so kills the tree; in other cases such Fungi attack the roots, and so induce rot and starvation of oxygen, resulting in fouling.

  • The extraordinary malformations known as Witches Brooms, caused by the repeated branching and tufting of twigs in which the mycelium of Exoascus (on birch) or Aecidium (on silver fir) are living, may be borne in considerable ntimbers for years without any very extensive apparent injury to the tree.

  • White or grey spots may be due to Peronospora, Erysiphe, Cystopus, Entyloma and other Fungi, the mycelium of which will be detected in the discoloured area; or they may be scale insects, or the results of punctures by Red-spider, &c. Yellow spots, and especially bright orange spots, commonly indicate Rust Fungi or other Uredineae; but Phyllosticta, Exoascus, Clasterosporium, Synchytrium, &c., also induce similar symptoms. Certain Aphides, Red-spider, Phylloxera and other insects also betray their presence by such spots.

  • This Fungus stimulates the main twig to shoot out more twigs than usual; the mycelium then enters each incipient twig and stimulates it to a repetition of the process, and so in the course of years large broom-like tufts result, often markedly different from the normal.

  • The fungus mycelium grows between the cuticle and the epidermis, the former being ultimately ruptured by numerous short branches bearing spores (conidia) by means of which the disease is spread.

  • In " Root rot," as the name implies, the roots are attacked, the fungus being a species of Ozonium, which envelops the roots in a white covering of mould or mycelium.

  • Portion of the mycelium of the fungus bearing spores (conidia), s, on erect branches, X250.

  • The disease is characterized by the appearance of a mycelium forming white or greyish-white patches on the young leaves; this spreads quickly and attacks the older leaves and branches, and ultimately reaches the grapes.

  • The disease spreads by the mycelium growing ever the epidermis of the plant.

  • The hyphae composing the mycelium are provided with haustoria which project into the cells of the affected part (fig.

  • A and B, mycelium (m), the mix t ure over the affe c ted with haustoria (h).

  • The mycelium spreads through the green parts of the plant, attacking the leaves, twigs and unripe grapes.

  • The mycelium of Sphaceloma grows just beneath the cuticle of the vine, through which it soon bursts, giving rise to a number of minute hyphae, which bear conidia.

  • Mycelium of the fungus attacking root of vine (reduced).

  • The hyphae of the mycelium of this fungus are septate, with numerous short branches.

  • 6), which forms subterranean strings of mycelium - so-called rhizomorphs.

  • The wood is nearly white, or of a yellowish tint, but sometimes exhibits blackish markings due to the mycelium of a fungus.

  • The mycelium produced from the spores dropped by the fungus or from the "spawn" in the soil, radiates outwards, and each year's successive crop of fungi rises from the new growth round the circle.

  • This prevents infection from outside and also destroys any spores or fungus mycelium that may have been packed away along with the bulbs.

  • By the fusion of the hyphae in the middle of the mycelium a pseudo-parenchymatous cortical layer has begun to form.

  • It any state most plants feed greedily upon it, and when pure or free from decaying wood or sticks it is a very safe ingredient in composts; but it is so liable to generate fungus, and the mycelium or spawn of certain fungi is so injurious to the roots of trees, attacking them if at all sickly or weakened by drought, that many cultivators prefer not' to mix leaf-mould with the soil used for permanent plants, as peaches or choice ornamental trees.

  • A widespread disease known as pocket-plums or bladderplums is due to an ascomycetous fungus, Exoascus pruni, the mycelium of which lives parasitically in the tissues of the host plant, passes into the ovary of the flower and causes the characteristic malformation of the fruit which becomes a deformed, sometimes curved or flattened, wrinkled dry structure, with a hollow occupying the place of the stone; the bladder plums are yellow at first, subsequently dingy red.

  • fungus, a mushroom), the botanical name covering in the broad sense all the lower cellular Cryptogams devoid of chlorophyll, which arise from spores, and the thallus of which is either unicellular or composed of branched or unbranched tubes or cell-filaments (hyphae) with apical growth, or of more or less complex wefted sheets or tissue-like masses of such (mycelium).

  • Mycelium with haustoria (h); 2, Erysiphe; A and B, mycelium (m), with haustoria (h).

  • In Arthrobotrys side-branches of the mycelium sling themselves around the host (Tylenchus) much as tendrils round a support.

  • As a rule the nuclei of the mycelium are very minute (1.5-2 µ in Phycomyces), but those of many asci and spores are large and easily rendered visible.

  • In some of the simpler fungi the spores are not borne on or in hyphae which can be distinguished from the vege A tative parts or mycelium, but in the vast majority of cases the sporogenous hyphae either ascend free into the air or radiate into the surrounding water as distinct branches, or are grouped into special columns, cushions, layers or complex masses obviously different in colour, consistency, shape and other characters from the parts which gather up and assimilate the food-materials.

  • The sporophore is obsolete when the spore-bearing hyphae are not sharply distinct from the mycelium, simple when the constituent hyphae are isolated, and compound when the latter are conjoined.

  • Much more complicated are the processes in a large series of "fructifications," where the mycelium first develops a densely packed mass of hyphae, all alike, in which labyrinths of cavities subsequently form by separation of hyphae in the previously homogeneous mass, and the hymenium covers the walls of these cavities and passages as with a lining layer.

  • Mycelium usually well developed, but sometimes poor or absent.

  • Mycelium present, antheridia with antherozoids, oogonium with single oosphere: Monoblepharidaceae.

  • Mycelium present; antheridia but no antherozoids; oogonia with one or more oospheres: Peronosporaceae, Saprolegniaceae.

  • Mycelium poorly developed or absent; oogonia and antheridia (without antherozoids) known in some cases; zoospores common: Chytridiaceae.

  • Mycelium well developed; sexual reproduction by zygospores; asexual reproduction by sporangia and conidia.

  • Life-history always very simple, no wellmarked alternation of generations; basidium borne directly on the mycelium.

  • In the rotting tissues branches of the older mycelium similarly swell up and form antheridia and oogonia (fig.

  • The other genera are more purely parasitic; the mycelium usually sends haustoria into the cells of the host and puts out branched, aerial conidiophores through the stomata, the branches of which abstrict numerous "conidia"; these either germinate directly or their contents break up into zoospores (fig.

  • Klebs has shown that the development of zoosporangia or of oogonia and pollinodia respectively in Saprolegnia is dependent on the external conditions; so long as a continued stream of suitable food-material is ensured the mycelium grows on without forming reproductive organs, but directly the supplies of nitrogenous and carbonaceous food fall below a certain degree of concentration sporangia are developed.

  • Those parts nearest the fly and best supplied develop barren hyphae only; in a zone at the periphery, where the products of putrefaction dissolved in the water form a dilute but easily accessible supply, the zoosporangia are developed in abundance; oogonia, however, are only formed in the depths of this radiating mycelium, where the supplies of available food materials are least abundant.

  • These parasitic and minute, chiefly aquatic, forms may be looked upon as degenerate Oomycetes, since a sexual process and feeble unicellular mycelium occur in some; or they may be regarded as series of primitive forms leading up to higher members.

  • In the first group zygospores can arise by the union of branches from the same mycelium and so can be produced by the growth from a single spore; this group includes Spordinia grandis, Spinellus fusiger, some species of Mucor, &c. The majority of forms, however, fall into the heterothallic group, in which the association of branches from two mycelia different in I nature is necessary for the 2, formation of zygospores.

  • The yeast-conidia, which bud off from the conidia or their resulting mycelium when sown in nutrient solutions, are developed in successive crops by budding exactly as in the yeast plant, but they cannot ferment sugar solutions.

  • When the flowers form, however, the mycelium sends hyphae into the young ovaries and rapidly replaces the stores of sugar and starch, &c., which would have gone to make the grain, by the soot-like mass of spores so well known as smut, &c. These spores adhere to the grain, and unless destroyed, by "steeping" or other treatment, are sown with it, and again produce sporidia and yeast-conidia which infect the seedlings.

  • mycelium is very much reduced in extent.

  • The asci are borne directly on the mycelium and are therefore fully exposed, being devoid from the beginning of any investment.

  • - The other divisions of the Ascomycetes may be distinguished as Carpoascomycetes because they do not bear the asci free on the mycelium but enclosed in definite fruit bodies or ascocarps.

  • The ordinary mycelium is the gametophyte since it hears the ascogonia and aritheridia when present; the cqe Two questions of great theoretical importance have been raised over and over again in connexion with yeasts, namely, (I) the morphological one as to whether yeasts are merely degraded forms of higher fungi, as would seem implied by their tendency to form elongated, hypha-like cells in the veils, and their development of "ascospores" as well as by the wide occurrence of yeast-like "sprouting forms" in other fungi (e.g.

  • m, Filaments of the mycelium cut transversely.

  • They form a superficial mycelium on the surface of the plant, the hyphae not usually penetrating the tissues but merely sending haustoria into the epidermal cells.

  • Only in rare cases is the mycelium intercellular.

  • (After De Bary.) A, Small portion of mycelium D, The perithecium.

  • (After Janczewski.) m, Mycelium.

  • The simpler forms bear the perithecia directly on the mycelium, but the more highly developed forms often bear them on a special mycelial development - the stroma, which is often of large size and special shape and colour, and of dense consistence.

  • When the sporidia infect a plant the mycelium so produced gives origin to aecidiospores and spermatia; the aecidiospores on infection produce a mycelium which bears uredospores and later teleutospores.

  • This is the lifehistory of the most complicated forms, of the so-called eu forms. In the opsis forms the uredospores are absent, the mycelium from the aecidiospores producing directly the teleutospores.

  • In brachy and hemi the aecidiospores are absent, the mycelium from the sporidia giving origin directly to the uredospores; the former possess spermatia, in the latter they are absent.

  • In lepto and micro forms both aecidiospores and uredospores are absent, the sporidia producing a mycelium which gives rise directly to teleutospores; in the lepto forms the teleutospores can germinate directly, in the micro forms only after a period of rest.

  • After this association the nuclei continue in the conjugate condition so s that the aecidiospores, the uredospore-bearing mycelium, the uredospores and the young teleutospores all contain two paired nuclei in their cells (fig.

  • In the hemi, brachy, micro and lepto forms, which possess no aecidium, we find that the association takes place at various points in the ordinary mycelium but always A, Portion of a young aecidium.

  • Whether B, Formation of the first sporethe association of nuclei in the mother-cell (sm), from the ordinary mycelium takes place basal cell (a) of one of the by the migration of a nucleus rows of spores.

  • There is also a further reduction in that the basidium is not derived from a teleutospore but is borne directly on the mycelium.

  • idium), a reduced fertilization which denotes their derivation, through the Uredineae, from more typically sexual forms. No one has yet t.-ade out in any form the exact way in which the association of nuclei tr -.-es place in the group. The mycelium is always found to contain conjugate nuclei before the formation of basidia, but the point at which the conjugate condition arises seems very variable.

  • mycelium ircdospores otachY' ar Mycelium aecidi'spores teleutospores (young) - mycelium SporoNtyte with conjugate nuclei GametohyEe with single nuclei teleutospores ?(mature) 8a ?; sporida ?m celium erm $ fertile cells Y sp (abortaitviae) (of aecidium) fertilized cells (of aecidium) and bears the basidiospores.

  • Exobasidium) the basidia are borne directly on the ordinary mycelium, but in the majority of cases the basidia are found developed in layers (hymenium) on special sporophores of characteristic form in the various groups.

  • In these sporophores (such as the well-known toadstools and mushrooms where the ordinary vegetative mycelium is underground) we have structures specially developed for bearing the basidiospores and protecting them from rain, &c., and for the distribution of the spores - see earlier part of article on distribution of spores (figs.

  • The underground mycelium in many cases spreads wider and wider each year, often in a circular manner, and the sporophores springing from it appear in the form of a ring - the so called fairy rings.

  • Nectria, Dasyscypha, &c.), or the enfeeblement of the tissues of the host, or invigoration of the fungus, the mycelium of which then becomes strong enough to overcome the host's resistance (Botrytis).

  • Such obligate parasites may be epiphytic (Erysipheae), the mycelium remaining on the outside and at most merely sending haustoria into the epidermal cells, or endophytic (Uredineae, Ustilagineae, &c.), when the mycelium is entirely inside the organs of the host.

  • An epiphytic fungus is not necessarily a parasite, however, as many saprophytes (moulds, &c.) germinate and develop a loose mycelium on living leaves, but only enter and destroy the tissues after the leaf has fallen; in some cases, however, these saprophytic epiphytes can do harm by intercepting light and air from the leaf (Fumago, &c.), and such cases make it difficult to draw the line between saprophytism and parasitism.

  • Endophytic parasites may be intracellular, when the fungus or its mycelium plunges into the cells and destroys their contents directly (Olpidium, Lagenidium, Sclerotinia, &c.), but they are far more frequently intercellular, at any rate while young, the mycelium growing in the lacunae between the cells (Peronospora, Uredineae) into which it may send short (Cystopus), or long and branched (Peronospora Calotheca) haustoria, or it extends in the middle lamella (Ustilago), or even in the solid substance of the cell-wall (Botrytis).

  • Similar gradations are observed in the direct effect of the parasite on the host, which may be local (Hemileia) when the mycelium never extends far from the point of infection, or general (Phytophthora) when it runs throughout the plant.

  • Trametes radiciperda attacks the roots and penetrates to the stem, causing rotting of the wood; the disease is difficult to eradicate, as the mycelium of the fungus travels from root to root in the soil.

  • These zoospores escape and swim about in any film of moisture, and on going to rest take a spherical form, germinate and produce threads of mycelium as at K.

  • The mycelium from the germinating sporangia or zoospores soon finds its way into the tissues of the potato leaf by the organs of transpiration, and the process of growth already described is repeated -over and over again till the entire potato leaf, or indeed the whole plant, is reduced to putridity.

  • The spores of the fungus pass the winter in the soil and the delicate mycelium attacks the young shoots in the summer.

  • The first signs of this fungus is the appearance of small white tufts of mycelium bursting through the skin of the tuber, the spores of the fungus being carried at the tips of the threads forming these tufts.

  • The ear loses its starch, and ceases to grow, and its ovaries become penetrated with the white spongy tissue of the mycelium of the fungus which towards the end of the season forms the sclerotium, in which state the fungus lies dormant through the winter.

  • The fine thread-like filaments composing the mycelium of the fungus are embedded in the tissue underneath and around the uredo-sorus, and draw from the host the nourishment required.

  • This had a hyaline mycelium bearing lemon-shaped sporangia which released motile zoospores after chilling in water, consistent with P. infestans.

  • As the mass grows it forms compact tufts that are collectively called a mycelium.

  • It is transmitted by wind-borne asexual spores and the dormant phase is as mycelium in dead leaf matter during frosty or dry summer conditions.

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