Pl. chalazæ. [mod.L., a. Gr. χάλαζα hail, any small lump or knot like a hail-stone. Cf. F. chalaze.]
1. Zool. Each of the two membranous twisted strings by which the yolk-bag of an egg is bound to the lining membrane at the ends of the shell, and kept near the middle of the albumen, with the germinating point uppermost; the tread or treadle.
1704. J. Harris, Lex. Techn., Chalaza, the Treadle of an Egg; every Egg has two of them … each Chalaza consists, as it were, of so many Hailstones separated from each other by that White.
1774. Goldsm., Nat. Hist. (1776), II. 29.
1841–71. T. R. Jones, Anim. Kingd., 786. An almost invisible membrane, the chalazæ, which, being twisted by the revolutions of the yelk, as it is pushed forward in the oviduct, is gathered into two delicate and spiral cords, whereby the yelk is retained in situ.
2. Bot. A spot on the seed where the nucleus joins the integuments.
1830. Lindley, Nat. Syst. Bot., 123. Raphe and chalaza usually very distinctly marked. Ibid., Introd. Bot. (1848), I. 398. This raphe … expands into a vascular dish or plate, which is called the chalaza.
1880. Gray, Struct. Bot., vi. § 8. 277. The proper base of the ovule … is the Chalaza…. In the simplest form of ovule, hilum and chalaza are one.
