[L. vitellus yolk of an egg.]
1. Embryol. The yolk of an egg; the germinative contents of an ovum-cell.
1728. Chambers, Cycl., s.v. Egg, In the middle of the inner White, is the Vitellus or Yelk.
1826. Good, Bk. Nat. (1834), I. 165. In this respect the albumen of the cotyledon corresponds with the vitellus of the hen’s egg.
1857. Berkeley, Cryptog. Bot., xv. 26. Nothing can be more close than the mode of development in these … and of the vitellus in the eggs of certain Mollusca.
1877. Huxley, Anat. Inv. Anim., 367. In certain Amphipods … the vitellus undergoes complete division.
2. Bot. A fleshy sac situated between the albumen and the embryo in a seed.
1807. J. E. Smith, Phys. Bot., 292. The Vitellus is esteemed by Gærtner to compose the bulk of the seed in Fuci, Mosses and Ferns.
1829. T. Castle, Introd. Bot., 245. The vitellus is an organ of a fleshy but firm texture, situated, when present, between the albumen and embryo.
1861. Bentley, Man. Bot., 444. Embryo minute, enclosed in a vitellus, and outside of abundant fleshy albumen.
b. (See quot.)
1900. B. D. Jackson, Gloss. Bot. Terms, Vitellus,… an oily substance adhering to the spores of Lycopodium.
