"There are intercrossing lines, so more hours were spent creating a structure on the metal surface that resembles the fabric," he explained.
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On the points of intercrossing the ribs are beaded. Moreover the whole shell is covered with growth-lines. The aperture is oblong, with a shallow sinus above, and a very short, wide siphonal canal below. The peristome is strong, crenulated, arched, below with a small sinus at the limit of the siphonal canal, interiorly with short grooves.
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Fertilisation of Orchids is a book by English naturalist Charles Darwin published on 15 May 1862 under the full explanatory title On the Various Contrivances by Which British and Foreign Orchids Are Fertilised by Insects, and On the Good Effects of Intercrossing. – Bibliographical introduction from: Freeman, R. B. (1977) The Works of Charles Darwin: An Annotated Bibliographical Handlist. 2nd edn. Dawson: Folkstone.
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Cerussite crystallizes in the orthorhombic system and is isomorphous with aragonite. Like aragonite it is very frequently twinned, the compound crystals being pseudo-hexagonal in form. Three crystals are usually twinned together on two faces of the prism, producing six-rayed stellate groups with the individual crystals intercrossing at angles of nearly 60°. Crystals are of frequent occurrence and they usually have very bright and smooth faces.
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He was concerned to show that biological variation exists both continuously, for some characters, and discontinuously for others, and coined the terms "meristic" and "substantive" for the two types. In common with Darwin, he felt that quantitative characters could not easily be "perfected" by the selective force of evolution, because of the perceived problem of the "swamping effect of intercrossing", but proposed that discontinuously varying characters could.
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In 1939, George Beadle demonstrated that the kernels of teosinte are readily "popped" for human consumption, like modern popcorn.NORMAN H. HOROWITZ, National Academy of Sciences. GEORGE WELLS BEADLE 1903–1989 (PDF) Some have argued it would have taken too many generations of selective breeding to produce large, compressed ears for efficient cultivation. However, studies of the hybrids readily made by intercrossing teosinte and modern maize suggest this objection is not well founded.
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The shell is reticulate (quite tight in the upper whorls, more expanded at the body whorl) with a granular, high mesh network produced by the intercrossing of vertical rounded, rather strong ribs and 3 strong decurrent cords. The body whorl is convex, slightly depressed toward the base, below the 5th and 6th ribs, which are stronger than the others. The aperture is elongated, narrow, with the same color as the shell. The columella is purplish.
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Fragaria × bringhurstii is a naturally occurring hybrid species of wild strawberry native to the West Coast of the United States. The species results from the natural intercrossing of Fragaria vesca and Fragaria chiloensis, native species whose ranges overlap in that region. All strawberries have a base haploid count of 7 chromosomes. Fragaria × bringhurstii is pentaploid, having 5 pairs of these chromosomes for a total of 35 chromosomes, 7 from the F. vesca parent, and 28 from the F. chiloensis parent.
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This lower part shows narrow, obtuse, axial ribs, occupying also the lower part of excavation, about 17 in number on the body whorl, where they are fainter near the aperture. These ribs are crossed by two strong spirals on the upper two whorls, three on the penultimate and numerous ones on the body whorl. The upper spiral forms a keel, which is tuberculiferous by the intercrossing of the ribs. Moreover there are fainter spirals in some of the interstices and just above the keel, in the basal part of the excavation, three in number in the penultimate whorl.
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Large surviving blight-resistant American chestnut in its natural range. Surviving trees passing resistance tests are utilized in ACCF's All American Breeding program. American Chestnut Cooperators Foundation (ACCF) is not using crosses with Asian species for blight resistance, but intercrossing among American chestnuts selected for native resistance to the blight, a breeding strategy described by the ACCF as "All-American intercrosses". John Rush Elkins, a research chemist and professor emeritus of chemistry at Concord University, and Gary Griffin, professor of plant pathology at Virginia Tech, think there may be several different characteristics which favor blight resistance.
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Elmer Swenson worked on a farm near Osceola, Wisconsin which he had inherited from his maternal grandfather Larson, an immigrant from Sweden. Swenson began breeding grapes in 1943, starting a program of intercrossing French hybrid grapes with selections of the local wild species, Vitis riparia. He was inspired by the work of T.V. Munson, a Texas breeder who had documented the American grape species and heavily utilized them in his breeding. Swenson hoped to generate seedlings capable of producing high quality fruit in his climate, something few if any cultivars could do reliably at that time.
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The whole basal part of the body whorl is spirally striated or grooved, the upper part of the whorls is nearly smooth, but for a few scarcely visible spirals and fine and coarse flexuous growth-lines, becoming much coarser on the siphonal canal, which by the intercrossing of this sculpture is slightly granular. The aperture is angular above, ending below in a rather long, narrow, slightly contorted siphonal canal. The peristome is thin, wdth a wide, shallow sinus above, strongly protracted in its median part. The columellar margin is strongly contorted, with a narrow, thin layer of enamel.
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In the third edition of his On the Origin of Species published in 1861, Charles Darwin added a Historical Sketch giving due credit to naturalists who had preceded him in publishing the opinion that species undergo modification, and that the existing forms of life have descended by true generation from pre-existing forms. According to Darwin: :The celebrated geologist and naturalist, Von Buch, in his excellent 'Description physique des Isles Canaries' (1836, p. 147), clearly expresses his belief that varieties slowly become changed into permanent species, which are no longer capable of intercrossing."The Origin of Species".
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Red Junglefowl, ancestor of domestic chickens, show that gene expression and methylation profiles in the thalamus and hypothalamus differed significantly from that of a domesticated egg laying breed. Methylation differences and gene expression were maintained in the offspring, depicting that epigenetic variation is inherited. Some of the inherited methylation differences were specific to certain tissues, and the differential methylation at specific loci were not altered much after intercrossing between Red Junglefowl and domesticated laying hens for eight generations. The results hint that domestication has led to epigenetic changes, as domesticated chickens maintained a higher level of methylation for more than 70% of the genes.
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In this book, he gave credence to Sprengel's ideas on the advantages of "intercrossing", and noted: "Many of our orchidaceous plants absolutely require the visits of moths to remove their pollen masses and thus to fertilise them". He introduced his new concept, the process of coevolution, describing the co-adaptation of bumblebees and red clover, and speculating "how a flower and a bee might slowly become, either simultaneously or one after the other, modified and adapted in the most perfect manner to each other, by the continued preservation of individuals presenting mutual and slightly favourable deviations of structure". This was a theme he developed in his orchid book.
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From his observations, Darwin surmised, in his 1862 publication On the Various Contrivances by Which British and Foreign Orchids Are Fertilized by Insects, and On the Good Effects of Intercrossing, that there must be a pollinator moth with a proboscis long enough to reach the nectar at the end of the spur. He arrived at this conclusion after attempting in vain to remove the pollinia of the flower using needles and bristles. Only after placing a cylinder with a diameter of of an inch (2.5 mm) down the full length of the spur was he able to detach the pollinia upon retracting it. The viscidium attached to the cylinder as he removed it.
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Darwin sent the incomplete manuscript to his publisher John Murray on 9 February 1862, while he was still working on the last chapter. Although anxious that the book might not sell, he could "say with confidence that the M.S. contains many new & very curious facts & conclusions". When the book was printed, he sent out presentation copies to all the individuals and societies who had helped him with his investigations, and to eminent botanists in Britain and abroad for review. On 15 May 1862 the book was published under the full title of On the Various Contrivances by Which British and Foreign Orchids Are Fertilised by Insects, and On the Good Effects of Intercrossing.
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The protoconch and subsequent whorls are eroded, remaining 4 whorls convex, angular, separated by a deep suture. The sculpture consists of axial ribs, rather remote on the upper whorls, 19 in number on penultimate whorl, nearly disappearing on the body whorl and numerous, raised striae or growth lines. These are crossed by spirals, of which a subsutural one is beaded, as well as those on the angle of keel ; above this latter are a few faint spirals and more numerous ones on lower part of whorls, 4 on penultimate, about 20 on the body whorl and siphonal canal, faintly beaded or crenuliferous at the points of intercrossing. The aperture is elongately oval, with a rather blunt angle above, ending below in a rather narrow siphonal canal.
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The American Chestnut Foundation is backcrossing blight-resistant Chinese chestnut into American chestnut trees, to recover the American growth characteristics and genetic makeup, and then finally intercrossing the advanced backcross generations to eliminate genes for susceptibility to blight.Valigra, Lori. "Back-Breeding Could Restore Chestnut Trees Ravaged by Blight". National Geographic News, December 29, 2005. Retrieved September 26, 2015. The first backcrossed American chestnut tree, called "Clapper", survived blight for 25 years, and grafts of the tree have been used by The American Chestnut Foundation since 1983. The Pennsylvania chapter of The American Chestnut Foundation, which seeks to restore the American chestnut to the forests of the Mid-Atlantic states, has planted over 22,000 trees."Planting and growing chestnut trees" . www.acf.org. Retrieved January 15, 2016.
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A recombinant inbred strain (or recombinant inbred line) is an organism with chromosomes that incorporate an essentially permanent set of recombination events between chromosomes inherited from two or more inbred strains. F1 and F2 generations are produced by intercrossing the inbred strains; pairs of the F2 progeny are then mated to establish inbred strains through long-term inbreeding. Families of recombinant inbred strains numbering from 25 to 5000 are often used to map the locations of DNA sequence differences (quantitative trait loci) that contributed to differences in phenotype in model organisms. Recombinant inbred strains or lines were first developed using inbred strains of mice but are now used to study a wide range of organisms – Saccharomyces cerevisiae (yeast), Zea mays (maize), barley, Drosophila melanogaster, C. elegans and rat.
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Darwin persevered with his orchids, and the book, On the various contrivances by which British and foreign orchids are fertilised by insects and the good effects of intercrossing, was published on 15 May 1862, just in time to give Wallace a copy on his return from the far East. While demonstrating that orchids evolve mechanisms that allow for cross- fertilisation, and offering strong evidence for Darwin's larger arguments about variation, the volume also countered natural theology in what Darwin himself admitted was a "flank movement against the enemy." By showing that the "wonderful contrivances" of the orchid have discoverable evolutionary histories, he countered claims by natural theologians that the organisms were examples of the perfect work of the Creator. His interest in orchids continued and he had a hot-house built at Down House, as well as experimenting with other seedlings and "slaving on bones of ducks and pigeon" and variations in other farmyard animals.
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