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annulus

annulus
1. One of a series of concentric rings or bands of varying width and opacity which are formed in the scales of bony fish. Winter rings are often narrower and denser than summer rings. The number of annuli is indicative of the age of a fish.

2. In the fruit bodies of certain agarics, a remnant of the partial veil that adheres as a ring of tissue around the stipe.

3. A ring of cells around the sporangium of some ferns. The walls of these cells become progressively thicker around the circumference, so inducing tension as they dehydrate, eventually causing the rupture of the sporangium (the point of breaking is called the stomium). The lid of the sporangium then curls back, releasing the tension induced by the annulus in a spring-like motion serving to aid spore dispersal.

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"annulus." A Dictionary of Ecology. . Encyclopedia.com. 15 Dec. 2017 <http://www.encyclopedia.com>.

"annulus." A Dictionary of Ecology. . Encyclopedia.com. (December 15, 2017). http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/annulus-0

"annulus." A Dictionary of Ecology. . Retrieved December 15, 2017 from Encyclopedia.com: http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/annulus-0

annulus

annulus
1. (in botany)
a. A ragged ring of tissue that remains on the stalk of a mushroom or toadstool. Also called a velum, it is formed from the ruptured membrane that originally covered the lower surface of the cap.

b. The region of the wall of a fern sporangium that is specialized for spore dispersal. It consists of cells that are thickened except on their outer walls. On drying out, the cells contract and the sporangium ruptures, releasing the spores. The annulus springs back into position when the residual water in the cells vaporizes and any remaining spores are dispersed.


2. (in zoology) Any of various ring-shaped structures in animals, such as any of the segments of an earthworm or other annelid.

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"annulus." A Dictionary of Biology. . Encyclopedia.com. 15 Dec. 2017 <http://www.encyclopedia.com>.

"annulus." A Dictionary of Biology. . Encyclopedia.com. (December 15, 2017). http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/annulus-3

"annulus." A Dictionary of Biology. . Retrieved December 15, 2017 from Encyclopedia.com: http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/annulus-3

annulus

annulus
1. In the fruit bodies of certain agarics, a remnant of the partial veil that adheres as a ring of tissue around the stipe.

2. A ring of cells around the sporangium of some ferns. The walls of these cells become progressively thicker around the circumference so inducing tension as they dehydrate, eventually causing the rupture of the sporangium. (The point of breaking is called the stomium.) The lid of the sporangium then curls back, releasing the tension induced by the annulus in a spring-like motion serving to aid spore dispersal.

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"annulus." A Dictionary of Plant Sciences. . Encyclopedia.com. 15 Dec. 2017 <http://www.encyclopedia.com>.

"annulus." A Dictionary of Plant Sciences. . Encyclopedia.com. (December 15, 2017). http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/annulus-1

"annulus." A Dictionary of Plant Sciences. . Retrieved December 15, 2017 from Encyclopedia.com: http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/annulus-1

annulus

annulus One of a series of concentric rings or bands of varying width and opacity which are formed in the scales of bony fish. Winter rings are often narrower and denser than summer rings. The number of annuli is indicative of the age of a fish.

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"annulus." A Dictionary of Zoology. . Encyclopedia.com. 15 Dec. 2017 <http://www.encyclopedia.com>.

"annulus." A Dictionary of Zoology. . Encyclopedia.com. (December 15, 2017). http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/annulus-2

"annulus." A Dictionary of Zoology. . Retrieved December 15, 2017 from Encyclopedia.com: http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/annulus-2

annulus

an·nu·lus / ˈanyələs/ • n. (pl. -li / -ˌlī/ ) technical a ring-shaped object, structure, or region.

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"annulus." The Oxford Pocket Dictionary of Current English. . Encyclopedia.com. 15 Dec. 2017 <http://www.encyclopedia.com>.

"annulus." The Oxford Pocket Dictionary of Current English. . Encyclopedia.com. (December 15, 2017). http://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/annulus

"annulus." The Oxford Pocket Dictionary of Current English. . Retrieved December 15, 2017 from Encyclopedia.com: http://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/annulus

annulus

annulus (planetary) A ring-like structure used, for example, to describe a discrete ring of ejecta around a martian rampart crater.

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"annulus." A Dictionary of Earth Sciences. . Encyclopedia.com. 15 Dec. 2017 <http://www.encyclopedia.com>.

"annulus." A Dictionary of Earth Sciences. . Encyclopedia.com. (December 15, 2017). http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/annulus

"annulus." A Dictionary of Earth Sciences. . Retrieved December 15, 2017 from Encyclopedia.com: http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/annulus

annulus

annulus (an-yoo-lŭs) n. (in anatomy) a circular opening or ring-shaped structure.
annular adj.

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"annulus." A Dictionary of Nursing. . Encyclopedia.com. 15 Dec. 2017 <http://www.encyclopedia.com>.

"annulus." A Dictionary of Nursing. . Encyclopedia.com. (December 15, 2017). http://www.encyclopedia.com/caregiving/dictionaries-thesauruses-pictures-and-press-releases/annulus

"annulus." A Dictionary of Nursing. . Retrieved December 15, 2017 from Encyclopedia.com: http://www.encyclopedia.com/caregiving/dictionaries-thesauruses-pictures-and-press-releases/annulus