Word Finder - hyphae

definition

Any of the long, threadlike filaments that form the mycelium of a fungus.

The internal tissue of the body of the solid higher Fungi, particularly the elongated stalks (stipes) of the fructifications of the Agarics, consists of hyphae running in a longitudinal direction, which no doubt serve for the conduction of organic food substances, just as do the trumpet-hyphae, similar in appearance, though not in origin, of the higher Brown Seaweeds.

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

The food so absorbed passes to the outer cortical mycellum, and from this tc the inner hyphae, which appear to be the organs of the interchangi of substance, for they are attracted to the neighborhood of thi nuclei of the cells, which they enter, and iii which they form agglom erations of interwoven filaments.

The inability to enter the cells may be due to the lack of chemotactic bodies, to incapacity to form cellulose-dissolving enzymes, to the existence in the hostcells of antagonistic bodies which neutralize or destroy the acids, enzymes or poisons formed by the hyphae, or even to the formation and excretion of bodies which poison the Fungus.

The mildew is in its turn attacked by a fungus of the same tribe, Cicinnobolus Cesatii, which lives parasitically within the hyphae of its host, and at times even succeeds in destroying it.

The segments of the hyphae in this group usually contain several nuclei.

A solid fungal body may usually be seen to consist of separate hyphae, but in some cases these are so bent and closely interwoven that an appearance like that of ordinary parenchymatous tissue is obtained in section, the structure being called pseudo parenchyrna.

On the under side of the leaf these patches are white and are composed of the spore-bearing hyphae.

The green (or blue-green) cells were termed gonidia by Wallroth, who looked upon them as asexual reproductive cells, but when it was later realized that they were not reproductive elements they were considered as mere outgrowths of the hyphae of the thallus which had developed chlorophyll.

The majority of the lichens, however, possess a stratified thallus in which the gonidia are found as a definite layer or layers embedded in a pseudoparenchymatous mass of fungal hyphae, i.e.

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

The exact relation of gonidia and hyphae has been investigated e specially by Bornet and also by Hedlund, and very considerable differences have been shown to exist in different genera.

In many other cases, especially those algae possessing Pleurococcus as their gonidia, there are no penetrating hyphae, but merely From Strasburger's Lehrbuck der Botanik, by permission of Gustav Fischer.

The soredia are found in a large number of lichens, and consist of a single gonidium or groups of gonidia, surrounded by a sheath and hyphae.

These were investigated by Tulasne in 1853, who gave them the name spermogonia The lower, ventral portion of the sperm09' gonium is lined by delicate hyphae, the sterigmata, which give origin to minute colourless cells, the spermatia.

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.

Clavaria mucida, however, h a s apparently some claims to be considered as a Basidiolichen, since the base of the fruit body and the thallus from which it arises, according to Coker, always shows a mixture of hyphae and algae.

The algal cells are usually controlled in their growth by the hyphae and are prevented from forming zoospores, and in some cases, as already described, the algal cells are killed sooner or later by the fungus.

The wall of the hyphae of the fungus give in the young state the ordinary reactions of cellulose but older material shows somewhat different reactions, similar to those of the so-called fungus-cellulose.

The spores, which may be unior multi-cellular, are either abstricted free from the ends of hyphae (acrogenous), or formed from segments in their course (chlamydospores) or from protoplasm in their interior (endogenous).

They extend back beyond the Carboniferous, where they occur as hyphae, &c., preserved in the fossil woods, but the best specimens are probably those in amber and in siliceous petrifactions of more recent origin.

Individual hyphae or their branches often exhibit specializations of form.

Many parasitic hyphae put out minute lateral branches, which pierce the cell-wall of the host and form a peg-like (Trichosphaeria), sessile (Cystopus), or stalked (Hemileia), knot-like, or_a B FIG.

In Rhizopus certain hyphae creep horizontally on the surface of the substratum, and then anchor their tips to it by means of a tuft of short branches (appressorium), the walls of which soften and gum themselves to it, then another branch shoots out from the tuft and repeats the process, like a strawberry-runner.

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 outermost hyphae may even put forth thinner hyphae, radiating into the soil like root-hairs, and the convergent tips may be closely appressed and so divided by septa as to resemble the root-apex of a higher plant (Armillaria mellea).

These reserve stores may be packed away in single hyphae or in swollen cells, but the hyphae containing them are often gathered into thick cords or mycelial strands (Phallus, mushroom, &c.), or flattened and anastomosing ribbons and plates, often containing several kinds of hyphae (Merulius lacrymans).

In other cases the strands undergo differentiation into an outer layer with blackened, hardened cell-walls and a core of ordinary hyphae, and are then termed rhizomorphs (Armillaria mellea), capable not only of extending the fungus in the soil, like roots, but also of lying dormant, protected by the outer casing.

Such aggregations of hyphae frequently become knotted up into dense masses of interwoven and closely packed hyphae, varying in size from that of a pin's head or a pea (Peziza, Coprinus) to that of a man's fist or head, and weighing io to 25 lb or more (Polyporus Mylittae, P. tumulosus, Lentinus Woermanni, P. Sapurema, &c.).

The interwoven hyphae fuse and branch copiously, filling up all interstices.

In many cases the swollen cell-walls serve as reserves, and sometimes the substance is so thickly deposited in strata as to obliterate the lumen, and the hyphae become nodular (Polyporus sacer, P. rhinoceros, Lentinus Woermanni).

The simpler mycelia consist of hyphae all alike and thin-walled, or merely differing in the diameter of the branches of various orders, or in their relations to the environment, some plunging into the substratum like roots, others remaining on its surface, and others (aerial hyphae) rising into the air.

Such hyphae may be multicellular, or they may consist of simple tubes with numerous nuclei and no septa (Phycomycetes), and are then non-cellular.

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

An epidermis-like or cortical protective outer layer is very common, and is usually characterized by the close septation of the densely interwoven hyphae and the thickening and dark colour of their outer walls (sclerotia, Xylaria, &c.).

Fibre-like hyphae with the lumen almost obliterated by the thick walls occur in mycelial cords (Merulius).

In Merulius lacrymans Hartig has observed thin-walled hyphae with large lumina, the septa of which are perforated like those of sieve-tubes.

The oidia of Erysipheae contain fibrosin bodies and the hyphae of Saprolegnieae cellulin bodies, but starch apparently never occurs.

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.

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.

Morphologically considered, spores are marked by peculiarities of form, size, colour, place of origin, definiteness in number, mode of preparation, and so forth, such that they can be distinguished more or less sharply from the hyphae which produce them.

The term "receptacle" sometimes applied to these spore-bearing _ hyphae is better replaced by sporophore.

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.

The chief distinctive characters of the sporogenous hyphae are their orientation, usually vertical; their limited apical growth; their peculiar branching, form, colour, contents, consistency; and their spore-production.

Compound sporophores arise when any of the branched or unbranched types of spore-bearing hyphae described above ascend into the air in consort, and are more or less crowded into definite layers, cushions, columns or other complex masses.

The same laws apply to the individual hyphae and their branches as to simple sporophores, and as long as the conidia, sporangia, gametes, &c., are borne on their external surfaces, it is quite consistent to speak of these as compound sporophores, &c., in the sense described, however complex they may become.

Among the simplest cases are the sheet-like aggregates of sporogenous hyphae in Puccinia, Uromyces, &c., or of basidia in Exobasidium, Corticium, &c., or of asci in Exoascus, Ascocorticium, &c. In the former, where the layer is small, it is often termed a sorus, but where, as in the latter, the sporogenous layer is extensive, and spread out more or less sheet-like on the supporting tissues, it is more frequently termed a hymenium.

Another simple case is that of the columnar aggregates of sporogenous hyphae in forms like Stilbum, Coremium, &c. These lead FIG.

Solenia, Cyphella - and even simpler cases are met with in Mortierella, where the zygospore is invested by the overgrowth of a dense mat of closely branching hyphae, and in Gymnoascus, where a loose mat of similarly barren hyphae covers in the tufts of asci as they develop.

In other cases (Diplodia, Aecidium, &c.) conidial or oidial "fructifications" arise by a number of hyphae interweaving themselves into a knot, as if they were forming a sclerotium.