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cone (in botany)

cone or strobilus (strŏb´ələs), in botany, reproductive organ of the gymnosperms (the conifers, cycads, and ginkgoes). Like the flower in the angiosperms (flowering plants), the cone is actually a highly modified branch; unlike the flower, it does not have sepals or petals. Usually separate male (staminate, or pollen) cones and female (ovulate, or seed) cones are borne on the same plant. Each of the numerous scales, or sporophylls, of the staminate cone bears pollen and each female-cone scale bears ovules in which egg cells are produced. In the pine, a conifer, the staminate cones are small and short-lived; they are borne in clusters at the top of the tree. At the time of pollination, enormous numbers of pollen grains are released and dispersed by wind; those that land accidentally on female-cone scales extend pollen tubes part way into the ovule during one growing season but usually do not reach the stage of actual fertilization until the next year. The cones that are commonly observed are the seed cones, which are normally hard and woody although in a few the scales are fleshy at maturity. The terms strobili and cones are also applied to the comparable and nonseed bearing structures of the horsetails and club mosses.

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"cone (in botany)." The Columbia Encyclopedia, 6th ed.. . Encyclopedia.com. 26 Jul. 2017 <http://www.encyclopedia.com>.

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cone

cone
1. (in botany) A reproductive structure occurring in gymnosperms, known technically as a strobilus. It consists of sporophylls bearing the spore-producing sporangia. Gymnosperms produce different male and female cones. The large woody female cones of pines, firs, and other conifers are made up of structures called ovuliferous scales, which bear the ovules. Cones are also produced by clubmosses and horsetails.

2. (in animal anatomy) A type of light-sensitive receptor cell, found in the retinas of all diurnal vertebrates. Cones are specialized to transmit information about colour (see colour vision) and are responsible for the visual acuity of the eye. They function best in bright light. They are not evenly distributed on the retina, being concentrated in the fovea and absent on the margin of the retina. Compare rod.

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"cone." A Dictionary of Biology. . Encyclopedia.com. 26 Jul. 2017 <http://www.encyclopedia.com>.

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"cone." A Dictionary of Biology. . Retrieved July 26, 2017 from Encyclopedia.com: http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/cone-1

cone

cone Solid, geometric figure swept out by a line (generator) that joins a point moving in a closed curve in a plane, to a fixed point (vertex) outside the plane. In a right circular cone, the vertex lies above the centre of a circle (base), and the cone's generators join the vertex to points on the circle. Such a cone has a volume 1/3πr2h and a curved surface area πrs, where h is vertical height, s the slant height, and r the radius of the base.

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"cone." World Encyclopedia. . Encyclopedia.com. 26 Jul. 2017 <http://www.encyclopedia.com>.

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cone

cone In a vertebrate eye, the less common (compare ROD) of the two types of light-receptor cell, which is sensitive only to relatively high levels of stimulation. Many cones are connected each to a single bipolar cell and thence to a ganglion cell whose axon forms a nerve fibre in the optic tract. Since cones respond only to high levels of stimulation and since each stimulation produces an individual nerve impulse, cones provide sharp images.

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"cone." A Dictionary of Zoology. . Encyclopedia.com. 26 Jul. 2017 <http://www.encyclopedia.com>.

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cone

cone An inflorescence of Coniferae. See also STROBILUS.

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"cone." A Dictionary of Plant Sciences. . Encyclopedia.com. 26 Jul. 2017 <http://www.encyclopedia.com>.

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"cone." A Dictionary of Plant Sciences. . Retrieved July 26, 2017 from Encyclopedia.com: http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/cone