from The American Heritage® Dictionary of the English Language, 4th Edition

  • n. Biology One of two spiral bands of tissue in an egg that connect the yolk to the lining membrane at either end of the shell.
  • n. Botany The region of an ovule that is opposite the micropyle, where the integuments and nucellus are joined.

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • n. A spiral band which attaches to the yolk of an egg, suspending it in the white
  • n. The location where the nucellus attaches to the integuments, opposite the micropyle.

from the GNU version of the Collaborative International Dictionary of English

  • n. The place on an ovule, or seed, where its outer coats cohere with each other and the nucleus.
  • n. A spiral band of thickened albuminous substance which exists in the white of the bird's egg, and serves to maintain the yolk in its position; the treadle.

from The Century Dictionary and Cyclopedia

  • n. In botany, that part of the ovule or seed where the integuments cohere with each other and with the nucleus. It is the true base of the seed, but corresponds to the hilum or scar only in some cases.
  • n. In zoology, one of the two albuminous twisted cords which bind the yolk-bag of an egg to the lining membrane at the two ends of the shell, and keep it near the middle as it floats in the albumen, so that the cicatricula or germinating point is always uppermost, and consequently nearest the source of heat during the process of incubation. Also called pullet-sperm and treadle.
  • n. Same as chalazion.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • n. one of two spiral bands of tissue connecting the egg yolk to the enclosing membrane at either end of the shell
  • n. basal part of a plant ovule opposite the micropyle; where integument and nucellus are joined


Greek khalaza, hard lump, hailstone.
(American Heritage® Dictionary of the English Language, Fourth Edition)
From Ancient Greek χάλαζα (chalaza, "hailstone, lump"). (Wiktionary)


  • I have been thinking that the apparent opening at the chalaza end must have been withering or perhaps gnawing by some very minute insects, as the ovarium is open at the upper end.

    More Letters of Charles Darwin — Volume 2

  • In two ovules there was an odd appearance, as if the outer coat of ovule at the chalaza end (if I understand the ovule) had naturally opened or withered where most of the pollen-tubes seemed to penetrate, which made me at first think this was a widely open foramen.

    More Letters of Charles Darwin — Volume 2

  • But here is an odd thing: they never once enter at (what I suppose to be) the "orifice," but generally at the chalaza ...

    More Letters of Charles Darwin — Volume 2

  • If you are very picky, you will want to remove the chalaza.

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  • The chalaza is composed of one or two spiral bands of tissue that suspend the yolk in the center of the white.

    Latest Articles

  • The entrance of pollen-tubes into the nucellus by the chalaza, instead of through the micropyle, was first fully demonstrated by Treub in his paper "Sur les

    More Letters of Charles Darwin — Volume 2


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  • Old Slavic zledica frozen rain, Persian zhaala hail. Either of a pair of spiral bands of thickened albuminous substance in the white of a bird's egg that extend out from opposite sides of the yolk to the ends of the egg and are there attached to the lining membrane.

    September 1, 2009