| 单词 | ascus |
| 例句 | In each ascus, two or more haploid ascospores fuse their nuclei in karyogamy. Fundamentals of Biology 2015-01-01T00:00:00Z That is, inside the ascus, a diploid fungal nucleus undergoes meiosis — or sexual, reductive cell division — to produce ascospores. How Ballistic Cup Fungi Fire Their Spores (and Look Cool Doing It) 2012-09-05T20:45:15.367Z The conclusion of the epitaph is perplexing: it states that her husband dedicated it to her and her son's memory—under "the axe"—"Sub asci� dedicavit." Notes and Queries, Vol. IV, Number 113, December 27, 1851 A Medium of Inter-communication for Literary Men, Artists, Antiquaries, Genealogists, etc. 2012-04-23T02:00:31.657Z Thallus septate; spores developed in special type of sporangium, the ascus, the number of spores being usually eight. Encyclopaedia Britannica, 11th Edition, Volume 11, Slice 3 "Frost" to "Fyzabad" 2011-08-15T02:00:28.473Z Exobasidiine�, a family of parasitic basidiomycetous Fungi, resembling the Exoascine� in most respects, but producing basidia in place of asci, a remarkable instance of parallel evolution. The New Gresham Encyclopedia Volume 4, Part 3: Estremoz to Felspar 2011-04-14T02:00:59.373Z Typically, an ascus is a cylindrical or club-shaped structure containing at maturity eight ascospores, which are usually liberated explosively and thereafter dispersed by the wind. The New Gresham Encyclopedia. Vol. 1 Part 2 Amiel to Atrauli A classic ascus is sausage-shaped, like this one, which belongs to a tasty morel mushroom, a type of large ascomycete with a compound cup head. How Ballistic Cup Fungi Fire Their Spores (and Look Cool Doing It) 2012-09-05T20:45:15.367Z Two of the asci and contained double spores, quite like those of a Lichen; much magnified. The Elements of Botany For Beginners and For Schools By this means the ascus cell is brought uppermost, and after the fusion of the two nuclei it develops enormously and produces the ascospores. Encyclopaedia Britannica, 11th Edition, Volume 11, Slice 3 "Frost" to "Fyzabad" 2011-08-15T02:00:28.473Z Exoascine�, a family of parasitic ascomycetous Fungi, distinguished by the absence of any definite fruit-body, the asci being produced in a layer on the surface of the host. The New Gresham Encyclopedia Volume 4, Part 3: Estremoz to Felspar 2011-04-14T02:00:59.373Z The term conidia he uses to designate the spores of imperfect fungi without perithecia or asci, such as the Hyphomycete� and the Melanconie�. Student's Hand-book of Mushrooms of America, Edible and Poisonous You can count the eight ascospores in this ascus: The tasty, tasty asci of a Morchella sp. How Ballistic Cup Fungi Fire Their Spores (and Look Cool Doing It) 2012-09-05T20:45:15.367Z Two asci of same, and contained spores, and accompanying filaments; more magnified. The Elements of Botany For Beginners and For Schools The asci are borne directly on the mycelium and are therefore fully exposed, being devoid from the beginning of any investment. Encyclopaedia Britannica, 11th Edition, Volume 11, Slice 3 "Frost" to "Fyzabad" 2011-08-15T02:00:28.473Z This small globule, the commencement of the receptacle, is not long in increasing, preserving its rounded form up to the development of the asci. Fungi: Their Nature and Uses The Hypog�i are analogous to the Tuberacei, except that the spores are not contained in asci as in the latter. Student's Hand-book of Mushrooms of America, Edible and Poisonous Some asci have elastic rings at their tips that only allow spores out once a set pressured is reached. How Ballistic Cup Fungi Fire Their Spores (and Look Cool Doing It) 2012-09-05T20:45:15.367Z These asci are crowded together side by side, and with them are slender empty asci called paraphyses. The Mushroom, Edible and Otherwise Its Habitat and its Time of Growth In the Helvellaceae there is no apothecium but a large irregular fruit body which at maturity bears the asci on its surface. Encyclopaedia Britannica, 11th Edition, Volume 11, Slice 3 "Frost" to "Fyzabad" 2011-08-15T02:00:28.473Z The asci are always present, the paraphyses are sometimes rare, and the mucilage in many cases seems to be entirely wanting. Fungi: Their Nature and Uses The paraphyses, when present, are at first very short, but they rapidly elongate, and are wholly developed before the appearance of the asci. Student's Hand-book of Mushrooms of America, Edible and Poisonous In ascomycetes that build their asci inside flask-like structures called perithecia or pseudothecia, the asci take turns snaking to the little opening, poking themselves out, and firing. How Ballistic Cup Fungi Fire Their Spores (and Look Cool Doing It) 2012-09-05T20:45:15.367Z The asci are cylindrical, opening by a lid. The Mushroom, Edible and Otherwise Its Habitat and its Time of Growth The basidium is a unicellular or multicellular structure from which four basidiospores arise as outgrowths; it starts as a binucleate structure, but soon, like the ascus, becomes uninucleate by the fusion of the two nuclei. Encyclopaedia Britannica, 11th Edition, Volume 11, Slice 3 "Frost" to "Fyzabad" 2011-08-15T02:00:28.473Z The paraphyses, which are formed at the first commencement of the receptacle, are at first very short, but soon elongate, and become wholly developed before the appearance of the asci. Fungi: Their Nature and Uses The term sporidia he limits to spores produced or enclosed in an ascus, as in the Ascomycete�. Student's Hand-book of Mushrooms of America, Edible and Poisonous But some discomycetes — fungi that produce their asci in a cup-like structure in which the fertile surface is completely exposed to the environment — have learned to synchronize their firing. How Ballistic Cup Fungi Fire Their Spores (and Look Cool Doing It) 2012-09-05T20:45:15.367Z The plants are small, sessile, or attached by a very short stem; closed at first, then expanding until nearly plane; disk yellow, smooth; asci clavate, 8 spored; spores hyaline, smooth. The Mushroom, Edible and Otherwise Its Habitat and its Time of Growth As mentioned before, the connexion between these two groups is very doubtful, and the derivation of the ascus from an ordinary sporangium of the Zygomycetes cannot be accepted. Encyclopaedia Britannica, 11th Edition, Volume 11, Slice 3 "Frost" to "Fyzabad" 2011-08-15T02:00:28.473Z The asci appear first at the base of the paraphyses, under the form of oblong cells, filled with colourless protoplasm. Fungi: Their Nature and Uses The sporidia are produced in membraneous asci, usually four or eight, or some multiple of that number, in each ascus; Cooke says "rarely four, most commonly eight." Student's Hand-book of Mushrooms of America, Edible and Poisonous In the diagram above, you can see the asci at various stages in meiosis. How Ballistic Cup Fungi Fire Their Spores (and Look Cool Doing It) 2012-09-05T20:45:15.367Z These asci are generally intermixed with slender, empty asci, or sterile cells, called paraphyses. The Mushroom, Edible and Otherwise Its Habitat and its Time of Growth According to his view, the ascus is in effect the sporangium with several spores, the conidium the sporangiole with but one spore, and that not loose but fused with the sporangiole wall. Encyclopaedia Britannica, 11th Edition, Volume 11, Slice 3 "Frost" to "Fyzabad" 2011-08-15T02:00:28.473Z This operculum may be the more readily seen when the ascus is coloured by a drop of tincture of iodine. Fungi: Their Nature and Uses He does not regard them as genuine asci, but as corresponding more to the peridium of the Gasteromycete� and Myxomycete�. Student's Hand-book of Mushrooms of America, Edible and Poisonous These sacs, or asci, are grouped together, lying side by side, forming the fruiting surface or hymenium, much as the basidia form the fruiting surface in the mushrooms. Studies of American Fungi. Mushrooms, Edible, Poisonous, etc. These asci are variously shaped bodies and are known in different orders by different names, such as ascoma, apothecium, perithecium, and receptacle. The Mushroom, Edible and Otherwise Its Habitat and its Time of Growth This mode of spore-formation is totally different from that in the ascus; hence one of the difficulties of the acceptance of Brefeld’s view of the homology of ascus and sporangium. Encyclopaedia Britannica, 11th Edition, Volume 11, Slice 3 "Frost" to "Fyzabad" 2011-08-15T02:00:28.473Z As in the Discomycetes, the hymenium consists of asci, paraphyses, and mucilage, but the whole forms a less compact and more gelatinous mass within the perithecium. Fungi: Their Nature and Uses Fruit, consisting of sporidia, mostly definite, contained in asci, springing from a naked or enclosed stratum of fructifying cells, and forming a hymenium.—Cooke and Berkeley. Student's Hand-book of Mushrooms of America, Edible and Poisonous In the latter species there are only two spores in an ascus. Studies of American Fungi. Mushrooms, Edible, Poisonous, etc. They usually have eight spores in each sac or ascus. The Mushroom, Edible and Otherwise Its Habitat and its Time of Growth The sporangium with its endogenous spores has been compared with an ascus, and on these grounds the group is placed among the Ascomycetes—a very doubtful association. Encyclopaedia Britannica, 11th Edition, Volume 11, Slice 3 "Frost" to "Fyzabad" 2011-08-15T02:00:28.473Z The formation and growth of the asci and sporidia differ little from what we have described, and when mature the asci dehisce, and the sporidia alone are ejected from the ostiolum. Fungi: Their Nature and Uses The asci differ in shape and size, according to the species. Student's Hand-book of Mushrooms of America, Edible and Poisonous The asci which disappear at at very early stage, are shown by Moeller as oval, each containing 8 spores. Synopsis of Some Genera of the Large Pyrenomycetes Camilla, Thamnomyces, Engleromyces Ascospore smooth or slightly wrinkled, free from the sides of the stem, attached at the tip of the stem, bell-shaped, thin; hymenium covering the entire surface of the ascospore; asci cylindrical, 8-spored. The Mushroom, Edible and Otherwise Its Habitat and its Time of Growth Carpoascomycetes.—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. Encyclopaedia Britannica, 11th Edition, Volume 11, Slice 3 "Frost" to "Fyzabad" 2011-08-15T02:00:28.473Z We are not aware that operculate asci have yet been detected. Fungi: Their Nature and Uses A characteristic of this species which distinguishes it from others of the same genus is found in the number of its sporidia, spores as seen in the ascus or spore sack. Student's Hand-book of Mushrooms of America, Edible and Poisonous Phylacia might be held distinct from Camillea on the ground of the powdery mass and the early disappearance of the perithecia and ascus walls. Synopsis of Some Genera of the Large Pyrenomycetes Camilla, Thamnomyces, Engleromyces It is very easily determined because all of its members develop their spores inside of small membranous sacs or asci. The Mushroom, Edible and Otherwise Its Habitat and its Time of Growth The asci may be derived from the terminal cell of the branches of the ascogenous hyphae, but usually they are derived from the penultimate cell, the tip curving over to form the so-called crozier. Encyclopaedia Britannica, 11th Edition, Volume 11, Slice 3 "Frost" to "Fyzabad" 2011-08-15T02:00:28.473Z These cysts are respectively known as sporangia, and asci or thecæ. Fungi: Their Nature and Uses Ascomycetes.—In the plants of this family the spores are not supported upon basidia, but instead are enclosed in minute sacs or asci formed from the fertile cells of a hymenium. Student's Hand-book of Mushrooms of America, Edible and Poisonous The mildews may be divided into two genera: Podosphæra, with a single ascus in the spore fruit; and Erysiphe, with two or more. Elements of Structural and Systematic Botany For High Schools and Elementary College Courses In morels these cells are elongated into cylindrical membranous sacs called asci, in each of which eight spores are usually developed. The Mushroom, Edible and Otherwise Its Habitat and its Time of Growth Other series of modifications arise in which the tissues corresponding to the stroma invest the sporogenous hyphal ends, and thus enclose the spores, asci, basidia, &c., in a cavity. Encyclopaedia Britannica, 11th Edition, Volume 11, Slice 3 "Frost" to "Fyzabad" 2011-08-15T02:00:28.473Z The number of sporidia contained in an individual ascus is usually less than in the majority of the Ascomycetes, and the sporidia approximate more nearly to the globose form. Fungi: Their Nature and Uses In some of the species, they become so gelatinized that they form a homogeneous mass about the asci, in which the individual paraphyses are no longer discernible. Ohio Biological Survey, Bull. 10, Vol. 11, No. 6 The Ascomycetes of Ohio IV and V It includes all the fungi that have the spores enveloped in delicate sacs called asci. Among the Mushrooms A Guide For Beginners For instance, in the asci of lichens there are formed from a portion of the protoplasm four or more small ascospores, which secrete a cell-wall and lie loose in the ascus. Scientific American Supplement, No. 531, March 6, 1886 The ordinary mycelium is the gametophyte since it bears the ascogonia and antheridia when present; the ascogenous hyphae with their asci represent the sporophyte since they are derived from the fertilized ascogonium. Encyclopaedia Britannica, 11th Edition, Volume 11, Slice 3 "Frost" to "Fyzabad" 2011-08-15T02:00:28.473Z The asci are produced in succession; the later, pressing themselves upwards between those previously developed, cause the rupture of the mature asci at the apex and the ejection of the sporidia with considerable force. Fungi: Their Nature and Uses Spores larger, usually 8 in each ascus, Spores hyaline. Ohio Biological Survey, Bull. 10, Vol. 11, No. 6 The Ascomycetes of Ohio IV and V Ascomycetes, or “Spore sac fungi,” where the spores are produced in delicate sacs called asci. Among the Mushrooms A Guide For Beginners They are set free by the rupture of the ascus, and germinate by putting out through their walls one or more filaments which branch and form the thallus of a new individual. Scientific American Supplement, No. 531, March 6, 1886 In the development of the ascus we find two nuclei at the base which fuse together to form the single nucleus of the young ascus. Encyclopaedia Britannica, 11th Edition, Volume 11, Slice 3 "Frost" to "Fyzabad" 2011-08-15T02:00:28.473Z Some of these are indefinite in the number contained in an ascus, although the majority are eight, and a few less. Fungi: Their Nature and Uses The mucilage forms itself almost at the same time as the paraphyses, and previous to the formation of the asci. Fungi: Their Nature and Uses This substance appears as a colourless or yellowish mucilage, which envelopes the paraphyses and asci, and so covers the hymenium with a shining coat. Fungi: Their Nature and Uses The mucilage also partly disappears, and the asci, attaining their maturity, become quite distinct, each enclosing its sporidia. Fungi: Their Nature and Uses The single nucleus divides by three successive divisions to form eight nuclei lying free in the protoplasm of the ascus. Encyclopaedia Britannica, 11th Edition, Volume 11, Slice 3 "Frost" to "Fyzabad" 2011-08-15T02:00:28.473Z Other species contain linear sporidia, which are often the length of the ascus, and may either be simple or septate. Fungi: Their Nature and Uses There is manifestly a succession in formation and maturity of the asci in a receptacle. Fungi: Their Nature and Uses The asci, after separation from the subhymenial tissue, continue to lengthen, or it may be that their elasticity permits of extension, during expulsion. Fungi: Their Nature and Uses The sporidia are usually four or eight, or some multiple of that number, in each ascus, rarely four, most commonly eight. Fungi: Their Nature and Uses The ascus is thus one of the most sharply characterized structures among the fungi. Encyclopaedia Britannica, 11th Edition, Volume 11, Slice 3 "Frost" to "Fyzabad" 2011-08-15T02:00:28.473Z The central cell becomes the single ascus, which is characteristic of the species, and the layer which surrounds it constitutes the inner wall of its perithecium. Fungi: Their Nature and Uses As they approach maturity, the sporidia accumulate towards the apex of the asci, and finally escape in the manner already indicated. Fungi: Their Nature and Uses In the interior of the receptacles, pear-shaped or ovate asci are formed in clusters, attached together at the base, and containing two or more hyaline sporidia. Fungi: Their Nature and Uses In the last family, the Ascomycetes, we shall meet with a very great variety of forms, all agreeing in producing sporidia contained in certain cells called asci, which are produced from the hymenium. Fungi: Their Nature and Uses Ascomycetes.—This, except in the case of a few of the simpler forms, is a very sharply marked group characterized by a special type of sporangium, the ascus. Encyclopaedia Britannica, 11th Edition, Volume 11, Slice 3 "Frost" to "Fyzabad" 2011-08-15T02:00:28.473Z The perfect sporidia are also very minute and numerous, being contained in asci borne in cups, which usually surround the spermogonia. Fungi: Their Nature and Uses In some of these, the asci are evanescent, but in the greater number are permanent. Fungi: Their Nature and Uses The features to be remembered in Perisporiacei, as forming the basis of their classification, are, that the asci are saccate, springing from the base of the perithecia, and are soon absorbed. Fungi: Their Nature and Uses Certain privileged cells of the hymenium swell, and ultimately become asci, enclosing a definite number of sporidia. Fungi: Their Nature and Uses The hymenium itself consists of elongated fertile cells, or asci, mixed with linear thread-like barren cells, called paraphyses, which are regarded by some authors as barren asci. Fungi: Their Nature and Uses New ampullas push themselves between those which are ripening and withering; a disc can, under favourable circumstances, always form new asci for weeks at a time. Fungi: Their Nature and Uses Each ascus contains a definite number of sporidia, which are sometimes coloured. Fungi: Their Nature and Uses When mature, the asci explode above, and the sporidia may be seen escaping like a miniature cloud of smoke in the light of the mid-day sun. Fungi: Their Nature and Uses The hymenium lines the inner walls of the perithecium, and forms a gelatinous nucleus, consisting of asci and paraphyses. Fungi: Their Nature and Uses When fully mature, the asci are ruptured and the sporidia escape by a pore which occupies the apex of the perithecium. Fungi: Their Nature and Uses The subhymenial tissue is composed of small compact cells, forming generally a more coloured and dense stratum, the superior cells of which give rise to the asci and paraphyses. Fungi: Their Nature and Uses The following are the technical characters of the family:— Fruit consisting of sporidia, mostly definite, contained in asci, springing from a naked or enclosed stratum of fructifying cells and forming a hymenium or nucleus = Ascomycetes. Fungi: Their Nature and Uses The sporidia are usually eight in each ascus, either arranged in single or double rows, or irregularly grouped together. Fungi: Their Nature and Uses The diffusion of the sporidia probably depends on the dissolution of the asci, and hence they will not be widely dispersed, unless, perhaps, by the action of rain. Fungi: Their Nature and Uses There may be other methods, and possibly the successive production of new asci may also be one, and the increase in bulk by growth of the sporidia another; but of this the evidence is scanty. Fungi: Their Nature and Uses Their special function seems still somewhat obscure, and Boudier suggests that they may be excitatory organs for the dehiscence of the asci. Fungi: Their Nature and Uses The Erysiphe which ultimately appears on the same mycelium consists of globose perithecia, externally furnished with thread-like appendages, and internally with asci containing sporidia. Fungi: Their Nature and Uses Still further examination will show that this fructification consists of cylindrical asci, each enclosing eight elliptical sporidia, closely packed together, and mixed with slender threads called paraphyses. Fungi: Their Nature and Uses The interior of the perithecium is occupied by a gelatinous nucleus, consisting of elongated cylindrical asci, each enclosing eight globose hyaline sporidia, with slender branched paraphyses. Fungi: Their Nature and Uses |
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