| 单词 | medullary ray |
| 例句 | Moreover, the living cells of the medullary rays exposed by the wound on the wood-surface also grow out under the released pressure, and form protruding callus pads on their own account. Disease in Plants 2012-03-01T03:00:22Z It is also traversed by medullary rays, Mr, which are continuations of those in the wood. Scientific American Supplement, No. 648, June 2, 1888. 2011-12-26T03:00:15.410Z The medullary rays usually consist of a single tier of cells, but in the Pinus type of wood broader medullary rays also occur and are traversed by horizontal resin-canals. Encyclopaedia Britannica, 11th Edition, Volume 12, Slice 7 "Gyantse" to "Hallel" 2011-12-26T03:00:11.613Z A longitudinal section made from bark to centre, as when a log is "quarter-sawed," shows a full side view of the "medullary rays." Trees Worth Knowing 2011-10-13T02:00:48.357Z As the tree grows larger, new, or secondary medullary rays start from the cambium then active, so that every year new rays are formed both thinner and shorter than the primary rays, Fig. Wood and Forest 2011-03-01T03:00:42.647Z Such healing may be rendered more certain by keeping the wounded surface moist—e.g. by means of damp moss, and so encouraging the formation of callus-bridges from the medullary rays. Disease in Plants 2012-03-01T03:00:22Z It is close-grained, free from knots, without apparent medullary rays, and is hard and tough, but will not take a polish. Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 3 "Electrostatics" to "Engis" 2011-02-06T03:00:53.093Z An anatomical peculiarity in the veins of Pinus and several other genera is the continuity of the medullary rays, which extend as continuous plates from one end of the leaf to the other. Encyclopaedia Britannica, 11th Edition, Volume 12, Slice 7 "Gyantse" to "Hallel" 2011-12-26T03:00:11.613Z Still later, the wedges filling the space, separated only by the thin lines, or medullary rays, running from pith to bark. The Elements of Botany For Beginners and For Schools Spruce is hardly distinguishable from fir, except by the existence of the resin ducts, and microscopically by the presence of tracheids in the medullary rays. Wood and Forest 2011-03-01T03:00:42.647Z Peridermium, the hyphae of which invade the medullary rays and resin canals and thus open the way to an outflow through cracks in the bark. Disease in Plants 2012-03-01T03:00:22Z As a permanent reserve food material, it occurs in seeds, in fruits, in tubers, in the pith, medullary rays and cortex of the stems of perennials, etc. The Chemistry of Plant Life The large medullary rays give to the wood a characteristic parenchymatous or lax appearance, which is in marked contrast to the more compact wood of a conifer. Encyclopaedia Britannica, 11th Edition, Volume 12, Slice 7 "Gyantse" to "Hallel" 2011-12-26T03:00:11.613Z Magnified view of surface of a bit of young Maple wood from which the bark has been torn away, showing the wood-cells and the bark-ends of medullary rays. The Elements of Botany For Beginners and For Schools MR, medullary rays, lines between the bundles connecting the pith and the cortex. Wood and Forest 2011-03-01T03:00:42.647Z In many of these cases the dying-back of the twigs is expedited owing to the mycelium invading the medullary rays and wood vessels, and so obstructing the transpiration current. Disease in Plants 2012-03-01T03:00:22Z It is said to be produced by the metamorphosis of the medullary rays under unfavorable conditions of growth. The Chemistry of Plant Life When tracheids occur in the medullary rays of the xylem these are replaced in the phloem-region by irregular parenchymatous cells known as albuminous cells. Encyclopaedia Britannica, 11th Edition, Volume 12, Slice 7 "Gyantse" to "Hallel" 2011-12-26T03:00:11.613Z The timber bears a striking resemblance to that of the oak, which has been mistaken for chestnut; but it may be distinguished by the numerous fine medullary rays. Encyclopaedia Britannica, 11th Edition, Volume 6, Slice 1 "Châtelet" to "Chicago" Its medullary rays," says Messrs. Lindley and Hutton, "appear to be more numerous, and frequently are not continued through one zone of wood to another, but more generally terminate at the concentric circles. The Cruise of the Betsey or, A Summer Ramble Among the Fossiliferous Deposits of the Hebrides. With Rambles of a Geologist or, Ten Thousand Miles Over the Fossiliferous Deposits of Scotland These conditions admit of four combinations, all of which appear in the medullary rays of Pinus, and of which a schematic representation is given in Plate VII. The Genus Pinus Annual rings well marked, medullary rays broad and prominent. Seasoning of Wood It is of interest to note that the leaves of Gnetum, while typically Dicotyledonous in appearance, possess a Gymnospermous character in the continuous and plate-like medullary rays of their vascular bundles. Encyclopaedia Britannica, 11th Edition, Volume 12, Slice 7 "Gyantse" to "Hallel" 2011-12-26T03:00:11.613Z If a striking contrast is wanted for the medullary rays of the quartering, apply a golden-oak stain first. Mission Furniture How to Make It, Part I These are the primary medullary rays, and connect the pith in the centre of the stem with the bark. Elements of Structural and Systematic Botany For High Schools and Elementary College Courses Tracheids of the medullary rays with smooth walls. The Genus Pinus Because of the broad medullary rays, it is generally "quarter-sawn" for cabinet work and furniture. Seasoning of Wood They all "rot" the timber by destroying its structure and substance, starting from the cambium and medullary rays. Scientific American Supplement, No. 643, April 28, 1888 If the force acts parallel to the axis of growth, the tracheids are more likely to be displaced if the marginal cells of the medullary rays are provided with weak walls that are readily compressed. The Mechanical Properties of Wood Including a Discussion of the Factors Affecting the Mechanical Properties, and Methods of Timber Testing The radiating lines are medullary rays. r, resin ducts. Elements of Structural and Systematic Botany For High Schools and Elementary College Courses Walls of the tracheids of the medullary rays dentate. The Genus Pinus It has broad medullary rays, and much of the timber has a beautiful figure. Seasoning of Wood Prof. Hartig lately showed me longitudinal radial sections of oak timber thus attacked, and the medullary rays showed up as glistening white plates. Scientific American Supplement, No. 643, April 28, 1888 The larger medullary rays are absent, but the smaller ones are often very distinct, with pores between them. Scientific American Supplement, No. 362, December 9, 1882 C, cross-section of a two-year-old branch at the point where the two growth rings join: I, the cells of the first year’s growth; II, those of the second year. m, a medullary ray, × 150. Elements of Structural and Systematic Botany For High Schools and Elementary College Courses The age is easily determined; the pith rays, or medullary rays, are also plain. Outlines of Lessons in Botany, Part I; from Seed to Leaf The characteristic "figure" of oak is due to the broad and deep medullary rays so conspicuous in this timber, and the same applies to honeysuckle. Seasoning of Wood It is important to note that some of these gigantic lycopods, which are classed with the CRYPTOGAMS, or flowerless plants, had pith and medullary rays dividing their cylinders into woody wedges. The Elements of Geology Such a process of petrifaction is still more remarkably exhibited in fossil wood, in which we often perceive not only the rings of annual growth, but all the minute vessels and medullary rays. The Student's Elements of Geology D, longitudinal section of a branch, showing the form of the tracheids and the bordered pits upon their walls. m, medullary ray, × 150. Elements of Structural and Systematic Botany For High Schools and Elementary College Courses The softwoods are made up chiefly of tracheids, or vertical cells closed at the ends, and of the relatively short parenchyma cells of the medullary rays which extend radially from the heart of the tree. Seasoning of Wood The sap in the tree descends through the bark, and except in early spring is not present in the wood of the tree except in the medullary rays and living tissues in the "sapwood." Seasoning of Wood The medullary rays, although present, are scarcely visible in most instances. Seasoning of Wood These bands or tiers of cell rows are the medullary rays or pith rays, and are common to all our lumber woods. Seasoning of Wood The large medullary rays of oak are often twenty and more cells wide, and several hundred cell rows in height, which amount commonly to one or more inches. Seasoning of Wood The porous spring-wood and radial gray tracts are partly composed of smaller vessels, but chiefly of tracheids, like those of pine, and of shorter cells, the "wood parenchyma," resembling the cells of the medullary rays. Seasoning of Wood Or, again, pronounced medullary rays further complicate the drying problem. Seasoning of Wood Rather close-grained, conspicuous medullary rays, and when quarter-sawn and well smoothed is very beautiful. Seasoning of Wood The medullary rays in birch are very fine and close and not easily seen. Seasoning of Wood The annual rings are very distinct, medullary rays very minute and not visible to the naked eye. Seasoning of Wood The annual rings are not distinctly marked, medullary rays fine and numerous. Seasoning of Wood The parenchyma cells of the medullary rays in oak do not cohere strongly and often check open, especially when steamed too severely. Seasoning of Wood Wood coarse-grained, well-marked annual rings, medullary rays few but broad. Seasoning of Wood This shell does not prevent the interior from drying, but when this drying occurs the interior is commonly checked along the medullary rays, commonly called "honeycombing" or "hollow-horning." Seasoning of Wood However, with some species, notably oak, surface cracks appear as a network of fine checks along the medullary rays. Seasoning of Wood |
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