| 单词 | archegonium |
| 例句 | Male antheridia and female archegonia grow at the tip of the stem. Fundamentals of Biology 2015-01-01T00:00:00Z The embryo develops inside the archegonium as the sporophyte. Concepts of Biology 2013-04-25T00:00:00Z The sperm and eggs are produced on gametophytes in antheridia and archegonia, and fertilization requires a thin film of water, so that the sperm can swim to the eggs. Miller & Levine Biology 2018-01-01T00:00:00Z They must swim, unaided, across an ephemeral film of water coating the nooks and crannies of mosses in search of an egg concealed within a protective structure called an archegonium. How Mosses Have Sex in Spite of Their Swimming-Challenged Sperm 2012-07-28T11:45:00.203Z Cryptogamous plants with a distinct axis or stem, growing from the apex, and commonly not with later increase in diameter, usually furnished with distinct leaves; reproduction by antheridia and archegonia, sometimes also by gemmation. The Manual of the Botany of the Northern United States Including the District East of the Mississippi and North of North Carolina and Tennessee 2012-04-12T02:00:30.140Z At fertilization, the sperm swims down the neck to the venter and unites with the egg inside the archegonium. Fundamentals of Biology 2015-01-01T00:00:00Z Many seedless plants produce sperm equipped with flagella that enable them to swim in a moist environment to the archegonia, the female gametangium. Concepts of Biology 2013-04-25T00:00:00Z The megaspore 763 is filled with tissue as in typical Gymnosperms, and from some of the superficial cells 3 to 5 archegonia are developed, characterized by long multicellular necks. Encyclopaedia Britannica, 11th Edition, Volume 12, Slice 7 "Gyantse" to "Hallel" 2011-12-26T03:00:11.613Z By dissecting the young buds, archegonia in all stages of growth may be found. Elements of Structural and Systematic Botany For High Schools and Elementary College Courses In germination they develop a minute prothallus which bears archegonia to be fertilized by antherozoids developed from the microspores. The Manual of the Botany of the Northern United States Including the District East of the Mississippi and North of North Carolina and Tennessee 2012-04-12T02:00:30.140Z The zygote, protected by the archegonium, divides and grows into a sporophyte, still attached by its foot to the gametophyte. Fundamentals of Biology 2015-01-01T00:00:00Z When the archegonium opens by the separation of the cells at the tip, the disorganized canal-cells escape, leaving a narrow tubular passage leading down to the ovum. Encyclopaedia Britannica, 11th Edition, Volume 4, Part 3 "Brescia" to "Bulgaria" The structure of the seed, the presence of two neck-cells in the archegonia, the late development of the embryo, the partially-fused cotyledons and certain anatomical characters, are features common to Ginkgo and the cycads. Encyclopaedia Britannica, 11th Edition, Volume 12, Slice 7 "Gyantse" to "Hallel" 2011-12-26T03:00:11.613Z G, young sporogonium still surrounded by the much enlarged base of the archegonium. h, neck of the archegonium. ar. abortive archegonia, × 12. Elements of Structural and Systematic Botany For High Schools and Elementary College Courses In the female plant there arise at the apex of the stem, surrounded by an envelope of ordinary leaves, several archegonia. Scientific American Supplement, No. 531, March 6, 1886 Flagellated sperm released from the antheridium swim on a wet surface to the archegonium, where the egg is fertilized. Fundamentals of Biology 2015-01-01T00:00:00Z Each antheridium or archegonium arises from a single cell, and while the mature structure is similar in the two groups, the development presents differences in liverworts and mosses. Encyclopaedia Britannica, 11th Edition, Volume 4, Part 3 "Brescia" to "Bulgaria" The tissue at the apex of the megaspore grows slightly above the level of the archegonia, so that the latter come to lie in a shallow depression. Encyclopaedia Britannica, 11th Edition, Volume 12, Slice 7 "Gyantse" to "Hallel" 2011-12-26T03:00:11.613Z Fig. 55.—Longitudinal section of a nearly full-grown sporogonium of Madotheca, which has not, however, broken through the overlying cells, × 25. sp. cavity in which the spores are formed. ar. abortive archegonium. Elements of Structural and Systematic Botany For High Schools and Elementary College Courses The sexual generation is a small green thalloid structure called a prothallium, which bears antheridia and archegonia, each archegonium having a neck-canal and oosphere, which is fertilized just as in the moss. Scientific American Supplement, No. 531, March 6, 1886 Many seedless plants produce sperm equipped with flagella that enable them to swim in a moist environment to the archegonia: the female gametangium. Fundamentals of Biology 2015-01-01T00:00:00Z A, Longitudinal section of thallus at the time of fertilization. an, Antheridia; ar, archegonia; in, involucre. Encyclopaedia Britannica, 11th Edition, Volume 4, Part 3 "Brescia" to "Bulgaria" Each megaspore may contain 2 to 6 archegonia. Encyclopaedia Britannica, 11th Edition, Volume 12, Slice 7 "Gyantse" to "Hallel" 2011-12-26T03:00:11.613Z B, young; C, nearly ripe archegonium of Funaria, optical section, × 150. Elements of Structural and Systematic Botany For High Schools and Elementary College Courses In mosses the flowers consist of a few special leaves surrounding or subtending organs called archegonia. The Gutenberg Webster's Unabridged Dictionary Section F, G and H The underside of the archegonial head contains protrusions called archegonia, which house the eggs. Fundamentals of Biology 2015-01-01T00:00:00Z It remains for long enclosed within the calyptra formed by the further development of the archegonial wall and surmounted by the neck of the archegonium. Encyclopaedia Britannica, 11th Edition, Volume 4, Part 3 "Brescia" to "Bulgaria" An archegonium consists of a large oval egg-cell surmounted by a short neck composed of one or more tiers of cells, six to eight cells in each tier. Encyclopaedia Britannica, 11th Edition, Volume 12, Slice 7 "Gyantse" to "Hallel" 2011-12-26T03:00:11.613Z Fig. 62.—A, young embryo of Funaria, still enclosed within the base of the archegonium, × 300. Elements of Structural and Systematic Botany For High Schools and Elementary College Courses I, vertical section of the female prothallium of Selaginella, × 50. ar. archegonium. Elements of Structural and Systematic Botany For High Schools and Elementary College Courses The gametophyte contains antheridia that produce, sperm and archegonia that produce eggs. Fundamentals of Biology 2015-01-01T00:00:00Z Other adaptations concern the protection of the sexual organs and sporogonia, and the retention of water in the neighbourhood of the archegonia to enable the spermatozoid to reach the ovum. Encyclopaedia Britannica, 11th Edition, Volume 4, Part 3 "Brescia" to "Bulgaria" The genus Ephedra, with its prothallus and archegonia, which are similar to those of other Gymnosperms, may be safely regarded as the most primitive of the Gnetales. Encyclopaedia Britannica, 11th Edition, Volume 12, Slice 7 "Gyantse" to "Hallel" 2011-12-26T03:00:11.613Z B, an older embryo freed from the archegonium, × 150. a, the apical cell. Elements of Structural and Systematic Botany For High Schools and Elementary College Courses J, section of an open archegonium, × 300. o, the egg cell. Elements of Structural and Systematic Botany For High Schools and Elementary College Courses Flagellated sperm swim to the archegonia and fertilize eggs. Fundamentals of Biology 2015-01-01T00:00:00Z In addition special involucres around the archegonia have arisen independently in several series. Encyclopaedia Britannica, 11th Edition, Volume 4, Part 3 "Brescia" to "Bulgaria" Finally the pollen tube penetrates down to and through the open neck of the archegonium, until it comes in contact with the egg cell. Elements of Structural and Systematic Botany For High Schools and Elementary College Courses As in the liverworts the young embryo is completely covered by the growing archegonium wall. Elements of Structural and Systematic Botany For High Schools and Elementary College Courses The female organ in the bryophytes is called an “archegonium,” and differs considerably from anything we have yet studied, but recalls somewhat the structure of the oögonium of Chara. Elements of Structural and Systematic Botany For High Schools and Elementary College Courses The female gametophyte is contained within a structure called the archegonium. Fundamentals of Biology 2015-01-01T00:00:00Z The archegonia are protected by being sunk in depressions of the disk or by a special two-lipped involucre. Encyclopaedia Britannica, 11th Edition, Volume 4, Part 3 "Brescia" to "Bulgaria" F, margin of one of the leaves surrounding the archegonia. Elements of Structural and Systematic Botany For High Schools and Elementary College Courses In this way it can be easily forced out of the archegonium, and then by thoroughly washing away the potash, neutralizing if necessary with a little acetic acid, very beautiful preparations may be made. Elements of Structural and Systematic Botany For High Schools and Elementary College Courses If a ripe archegonium is placed in water, it soon opens at the top, and the contents of the canal cells are forced out, leaving a clear channel down to the egg cell. Elements of Structural and Systematic Botany For High Schools and Elementary College Courses Just before the spores are ripe, the stalk of the sporogonium elongates rapidly, carrying up the capsule, which breaks through the archegonium wall, and finally splits into four valves, and discharges the spores. Elements of Structural and Systematic Botany For High Schools and Elementary College Courses In the Acrogynous Jungermanniaceae the plant is throughout foliose, and the archegonia occupy the ends of the main shoot or of its branches. Encyclopaedia Britannica, 11th Edition, Volume 4, Part 3 "Brescia" to "Bulgaria" The first wall in the embryo is nearly at right angles to the axis of the archegonium and divides the egg cell into nearly equal parts. Elements of Structural and Systematic Botany For High Schools and Elementary College Courses G, H, young archegonia, in optical section, × 150. o, central cell. b, ventral canal cell. c, upper canal cell. Elements of Structural and Systematic Botany For High Schools and Elementary College Courses The first divisions of the fertilized egg cell resemble those in the moss embryo, except that the first wall is parallel with the archegonium axis, instead of at right angles to it. Elements of Structural and Systematic Botany For High Schools and Elementary College Courses Fig. 67.—A, embryo of the ostrich fern just before breaking through the prothallium, × 50. st. apex of stem. l, first leaf. r, first root. ar. neck of the archegonium. Elements of Structural and Systematic Botany For High Schools and Elementary College Courses The small thallus bears the antheridia and archegonia, each of which is surrounded by a tubular involucre, on the upper surface of distinct individuals. Encyclopaedia Britannica, 11th Edition, Volume 4, Part 3 "Brescia" to "Bulgaria" The archegonia have a shorter neck than those of the ferns, and the neck is straight. Elements of Structural and Systematic Botany For High Schools and Elementary College Courses I, a ripe archegonium in the act of opening, × 150. o, egg cell. Elements of Structural and Systematic Botany For High Schools and Elementary College Courses In the seed plants the macrosporangia remain attached to the parent plant, in nearly all cases, until the archegonia are fertilized and the embryo plant formed. Elements of Structural and Systematic Botany For High Schools and Elementary College Courses After the archegonia are fertilized the outer parts of the ovule become hard and brown, and serve to protect the embryo plant, which reaches a considerable size before the sporangium falls off. Elements of Structural and Systematic Botany For High Schools and Elementary College Courses Longitudinal section of the summit of a shoot bearing a nearly mature sporogonium, sg, still enclosed in the calyptra; ar′, archegonia which have remained unfertilized; st, stem; b, leaf; p, perianth. Encyclopaedia Britannica, 11th Edition, Volume 4, Part 3 "Brescia" to "Bulgaria" In the upper part of the prothallium several large archegonia are formed in much the same way as in the pteridophytes. Elements of Structural and Systematic Botany For High Schools and Elementary College Courses In studying the development of the antheridia, it is only necessary to mount the plants in water and examine them directly; but the study of the archegonia requires careful longitudinal sections of the prothallium. Elements of Structural and Systematic Botany For High Schools and Elementary College Courses The necks of the archegonia hardly project above the general surface of the thallus. Encyclopaedia Britannica, 11th Edition, Volume 4, Part 3 "Brescia" to "Bulgaria" The young sporogonium is protected by a thick calyptra derived from the tissue of the thallus around the archegonium. Encyclopaedia Britannica, 11th Edition, Volume 4, Part 3 "Brescia" to "Bulgaria" The archegonia are borne at the apex of the main stem or of a lateral branch. Encyclopaedia Britannica, 11th Edition, Volume 4, Part 3 "Brescia" to "Bulgaria" The sexual organs are developed in groups at the apices, the antheridial group usually terminating the main axis while the archegonia are borne on a lateral branch. Encyclopaedia Britannica, 11th Edition, Volume 4, Part 3 "Brescia" to "Bulgaria" Under favorable conditions, the first antheridia are ripe in about five weeks; the archegonia, which are borne on separate plants, a few weeks later. Elements of Structural and Systematic Botany For High Schools and Elementary College Courses Their general similarity to the mature antheridia and archegonia of liverworts and the main difference in their development have been referred to. Encyclopaedia Britannica, 11th Edition, Volume 4, Part 3 "Brescia" to "Bulgaria" The female plant is rather more highly organized, consisting of a short stem bearing a few leaves around the group of archegonia. Encyclopaedia Britannica, 11th Edition, Volume 4, Part 3 "Brescia" to "Bulgaria" |
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