1. The yelk of an egg. [See Yelk.]
2. The unctuous secretion from the skin of sheep, which renders the pile soft and pliable.
3. The vitellus, a part of the seed of plants, so named by Gaertner, from its supposed analogy with the yelk of an egg. It is characterized as very firmly and inseparably connected with the embryo, yet never rising out of the integuments of the seed in germination, but absorbed, like the albumen, (see White and Perisperm, ) for the nourishment of the embryo. When the albumen is present, it is always situated between it and the embryo. In the grasses it forms a scale between the embryo and albumen. It is considered by Smith as a subterraneous cotyledon.